FIRST SOUTH AMERICAN AGATHIS (ARAUCARIACEAE), EOCENE OF PATAGONIA

Ari  Iglesias; Kirk Johnson

The Southern Hemisphere may have provided biodiversity refugia after the Cretaceous/Palaeogene (K/Pg) mass extinction. However, few extinction and recovery studies have been conducted in the terrestrial realm using well-dated macrofossil sites that span the latest Cretaceous (late Maastrichtian) and early Palaeocene (Danian) outside western interior North America (WINA). Here, we analyse insect-feeding damage on 3,646 fossil leaves from the latest Maastrichtian and three time slices of the Danian in Chubut, Patagonia, Argentina (palaeolatitude approximately 50° S). We test the southern refugial hypothesis and the broader hypothesis that the extinction and recovery of insect herbivores, a central component of terrestrial food webs, differed substantially from WINA at locations far south of the Chicxulub impact structure in Mexico. We find greater insect-damage diversity in Patagonia than in WINA during both the Maastrichtian and Danian, indicating a previously unknown insect richness. As in WINA, the total diversity of Patagonian insect damage decreased from the Cretaceous to the Palaeocene, but recovery to pre-extinction levels occurred within approximately 4 Myr compared with approximately 9 Myr in WINA. As for WINA, there is no convincing evidence for survival of any of the diverse Cretaceous leaf miners in Patagonia, indicating a severe K/Pg extinction of host-specialized insects and no refugium. However, a striking difference from WINA is that diverse, novel leaf mines are present at all Danian sites, demonstrating a considerably more rapid recovery of specialized herbivores and terrestrial food webs. Our results support the emerging idea of large-scale geographic heterogeneity in extinction and recovery from the end-Cretaceous catastrophe.

A late Oligocene plant macrofossil assemblage is described from the Río Leona Formation, Argentinian Patagonia. This includes a fern, “Blechnum” turbioense Frenguelli, one species of conifer, and sixteen angiosperm taxa. Rosaceae, Myrtaceae, Proteaceae, Lauraceae, Anacardiaceae and Typhaceae are represented by one species in each family. Five species are considered to be members of the Fabales. Three leaf taxa together with Carpolithus seeds are placed in the Nothofagaceae. Palynomorphs and permineralized woods complete the floral record of the Río Leona Formation, which is considered early late Oligocene based on radiometric dating and palynofloras.

Paleobiology, 2020, pp. 1–25 DOI: 10.1017/pab.2020.45 Article Cretaceous–Paleogene plant extinction and recovery in Patagonia Elena Stiles , Peter Wilf, Ari Iglesias, María A. Gandolfo, and N. Rubén Cúneo Abstract.—The Cretaceous–Paleogene (K/Pg) extinction appears to have been geographically heterogeneous for some organismal groups. Southern Hemisphere K/Pg palynological records have shown lower extinction and faster recovery than in the Northern Hemisphere, but no comparable, well-constrained Southern Hemisphere macroﬂoras spanning this interval had been available. Here, macroﬂoral turnover patterns are addressed for the ﬁrst time in the Southern Hemisphere, using more than 3500 dicot leaves from the latest Cretaceous (Maastrichtian) and the earliest Paleocene (Danian) of Argentine Patagonia. A maximum ca. 90% macroﬂoral extinction and ca. 45% drop in rareﬁed species richness is estimated across the K/Pg, consistent with substantial species-level extinction and previously observed extirpation of host-specialized leaf mines. However, prior palynological and taxonomic studies indicate low turnover of higher taxa and persistence of general ﬂoral composition in the same sections. High species extinction, decreased species richness, and homogeneous Danian macroﬂoras across time and facies resemble patterns often observed in North America, but there are several notable differences. When compared with boundary-spanning macroﬂoras at similar absolute paleolatitudes (ca. 50°S or 50°N) from the Williston Basin (WB) in the Dakotas, both Maastrichtian and Danian Patagonian species richnesses are higher, extending a history of elevated South American diversity into the Maastrichtian. Despite high species turnover, our analyses also reveal continuity and expansion of leaf morphospace, including an increase in lobed and toothed species unlike the Danian WB. Thus, both Patagonian and WB K/Pg macroﬂoras support a signiﬁcant extinction event, but they may also reﬂect geographically heterogeneous diversity, extinction, and recovery patterns warranting future study. Elena Stiles. *Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, U.S.A. E-mail: estiles@uw.edu. *Present address: Department of Biology, University of Washington, Seattle, Washington 98105, U.S.A. Peter Wilf. Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802, U.S.A. E-mail: pwilf@psu.edu Ari Iglesias. Consejo Nacional de Investigaciones Cientíﬁcas y Técnicas (CONICET)–Universidad Nacional del Comahue INIBIOMA, San Carlos de Bariloche 8400, Río Negro, Argentina. E-mail: ari_iglesias@yahoo.com.ar María Alejandra Gandolfo. L.H. Bailey Hortorium, Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14853, U.S.A. E-mail: mag4@cornell.edu N. Rubén Cúneo. Consejo Nacional de Investigaciones Cientíﬁcas y Técnicas (CONICET)–Museo Paleontológico Egidio Feruglio, Avenida Fontana 140, Trelew 9100, Chubut, Argentina. E-mail: rcuneo@mef.org.ar Accepted: 27 August 2020 Data available from the Dryad Digital Repository: https://doi.org/10.5061/dryad.jsxksn071 Introduction The devastating environmental consequences of the end-Cretaceous bolide impact affected both marine and terrestrial organisms (e.g., Alvarez et al. 1980; Prinn and Fegley 1987; Robertson et al. 2013; Vellekoop et al. 2014; Tyrrell et al. 2015; Artemieva and Morgan 2017; Brugger et al. 2017). Over 60% of Cretaceous species became extinct, making the Cretaceous–Paleogene (K/Pg) event the most recent of the “big ﬁve” mass extinctions (Raup and Sepkoski 1982; Jablonski 2005; Schulte et al. 2010). Although the K/Pg event affected biotas globally, the severity of the extinction and the pacing of the recovery were geographically heterogeneous for some groups of organisms (see next paragraph). Modern biodiversity is shaped by the surviving lineages of the K/Pg (e.g., Erwin 2002; Krug et al. 2017), establishing today’s biogeographic patterns, in part, as the legacy of a globally heterogeneous extinction (e.g., Wolfe 1987). Southern Hemisphere records of calcareous nannoplankton, insect herbivory, and terrestrial palynomorphs indicate lower extinction and/or faster recoveries than Northern © The Author(s), 2020. Published by Cambridge University Press on behalf of The Paleontological Society.0094-8373/20 Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 2 ELENA STILES ET AL. Hemisphere counterparts (Vajda et al. 2001; Vajda and Raine 2003; Iglesias et al. 2007; Pole and Vajda 2009; Jiang et al. 2010; Barreda et al. 2012; Cantrill and Poole 2012; Schueth et al. 2015; Donovan et al. 2016). Furthermore, several plant and vertebrate groups that had been known only from Mesozoic localities in the Northern Hemisphere, have been reported in Cenozoic Southern Hemisphere deposits suggesting that they survived the K/Pg in southern latitudes (Case and Woodburne 1986; Pascual et al. 1992; Bonaparte et al. 1993; Goin et al. 2006, 2012; McLoughlin et al. 2008, 2011; Gelfo et al. 2009; Sterli and de la Fuente 2019). Proposed explanations for this geographic heterogeneity (Jiang et al. 2010; Donovan et al. 2016, 2018) have referenced increased distance from the Mexican impact site (Schulte et al. 2010), oceanic buffering of impact winter temperatures in the Southern Hemisphere (Bardeen et al. 2017; Tabor et al. 2020), and a bolide impact angle that would have directed most ejecta and debris northward (Schultz and D’Hondt 1996). Because plants are the primary producers in terrestrial ecosystems and one of the most biodiverse groups of organisms, the paleobotanical record is critical for understanding extinction events on land (e.g., Nichols and Johnson 2008). However, the vast majority of plant-bearing K/Pg continental sites is concentrated in the western interior of North America (NAM), which bears numerous examples of stratigraphically and temporally well constrained boundary-spanning palynoﬂoras (e.g., Nichols et al. 1986; Nichols and Fleming 1990; Sweet et al. 1990, 1999; Sweet and Braman 2001; Nichols 2002; Bercovici et al. 2009) and macroﬂoras (e.g., Wolfe and Upchurch 1986; Johnson et al. 1989; Johnson and Hickey 1990; Johnson 1992, 2002; Upchurch 1995; Barclay et al. 2003; Nichols and Johnson 2008). Southern Hemisphere K/Pg-spanning paleoﬂoras are scarce and have been primarily limited to palynological records (e.g., Vajda-Santivanez 1999; Vajda et al. 2001; Vajda and Raine 2003; Pole and Vajda 2009; Barreda et al. 2012; Cantrill and Poole 2012; Scasso et al. 2020). Cretaceous–Paleogene macroﬂoras from New Zealand revealed a dramatic ﬂoral turnover (Pole and Vajda 2009) and a paleoclimatic cooling trend consistent with global records (Kennedy et al. 2002) across the K/Pg, but the severity of the macroﬂoral extinction was not estimated. Until now, no well-constrained and well-sampled macroﬂoral Maastrichtian and Danian sites from the same region have been available in the Southern Hemisphere. Recent studies of the latest Cretaceous (Maastrichtian) Leﬁpán and early Paleocene (Danian) Salamanca and Peñas Coloradas Formations of Chubut, Argentine Patagonia (Fig. 1; and see “Materials” and “Analytical Methods”) showed lower palynological extinction, faster recovery of insect herbivory damage-type diversity, and remarkably diverse Danian macroﬂoras compared with most NAM sections of the same ages. Speciﬁcally, spore and pollen records showed <10% extinction across the K/Pg compared with the 30%–40% extinction in NAM palynoﬂoras (Nichols and Fleming 1990; Sweet and Braman 2001; Hotton 2002; Nichols 2002; Barreda et al. 2012). Notably, in early Danian Patagonian pollen records, an abundance spike of the conifer Classopollis represents the last record of a genus that is otherwise only known until the Late Cretaceous worldwide (Barreda et al. 2012). Insect feeding-damage types on angiosperm leaves recovered to pre-K/Pg diversity levels within about 4 Myr, compared with the estimated ca. 9 Myr for NAM (Donovan et al. 2016, 2018), and Danian macroﬂoras of the Salamanca Formation are much more diverse than most coeval NAM counterparts, suggesting a faster-paced Patagonian recovery (Iglesias et al. 2007). However, comparable Maastrichtian leaf ﬂoras from the same Patagonian region have not yet been evaluated using similar methods. Gymnosperm macrofossils of the Leﬁpán and Salamanca Formations have been the subject of taxonomic studies (Zamuner et al. 2000; Brea et al. 2005; Quiroga et al. 2015; Ruiz et al. 2017; Wilf et al. 2017; AndruchowColombo et al. 2018, 2019; Escapa et al. 2018), indicating the survival of the Podocarpaceae and Araucariaceae conifer families. The presence of several derived angiosperm groups known from reproductive material in the Salamanca Formation suggests that they also represent K/Pg survivor families (Iglesias et al. 2007; Raigemborn et al. 2009; Jud et al. Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION 2017, 2018a,b; Supplementary Tables 1, 2). Angiosperm leaf fossils have sourced the aforementioned work on K/Pg insect damage (Donovan et al. 2016, 2018), yet the extensive leaf collections on which the insect herbivory was documented have not been rigorously compared to quantify macroﬂoral species extinction in Patagonia across the Cretaceous/ Paleogene transition. Fossil dicot leaves from the Maastrichtian and Danian of Patagonia (Fig. 1) together offer insight into macroﬂoral K/Pg diversity, and potential extinction and recovery patterns with well-sampled, stratigraphically and temporally constrained collections for the ﬁrst time in the Southern Hemisphere (Iglesias et al. 2007; Scasso et al. 2012; Clyde et al. 2014; Donovan et al. 2016, 2018). Through the analysis of more than 3500 leaf fossils from four localities, this study addresses terminal Cretaceous and early Paleocene macroﬂoral diversity in Patagonia, and the possible effects of the K/Pg extinction event on the ﬂoras of the region while considering the potential climatic, sampling, and ecological biases impacting the observations. Although the main goal of this contribution is to document the ﬁrst temporally constrained K/Pg-spanning macroﬂoral assemblages occurring within the same region in the Southern Hemisphere, we compare our results with the well-sampled, boundary-spanning K/Pg NAM macroﬂoras from similar absolute paleolatitudes (ca. 50°N or 50°S) in the Williston Basin (WB) in North Dakota (Johnson 2002; Wilf and Johnson 2004) to further explore potential biases in our observations and to examine potential geographic heterogeneity in macroﬂoral patterns among two widely separated regions. Materials The collections studied here are primarily the same as those from Chubut, Argentina, used in earlier work on Danian ﬂoral diversity (e.g., Iglesias 2007; Iglesias et al. 2007) and K/Pg insect damage (Donovan et al. 2016, 2018), plus some additional material previously not cataloged (Supplementary Table 3). Iglesias et al. (2007) documented Danian dicot-leaf diversity by morphotyping and assigning 3 systematic afﬁnities when possible (Iglesias 2007; Iglesias et al. 2007; more recent updates shown in Supplementary Table 1). Donovan et al. (2016, 2018) analyzed the insect feedingdamage diversity on the leaves from Maastrichtian and Danian collections and proposed a preliminary morphotype classiﬁcation for the Maastrichtian leaves. The leaf collections from the Leﬁpán (Maastrichtian) and Salamanca and Peñas Coloradas (Danian) Formations were compiled over a series of ﬁeld trips involving the four junior authors and others since 2003, and they are curated in the Paleobotanical Collection of the Museo Paleontológico Egidio Feruglio (MEF; repository acronym MPEF-Pb), Trelew, Argentina (Supplementary Table 3). All collections studied are unbiased, complete census collections of all identiﬁable material found, taken to the lab at MEF, and vetted and tallied. Although they are separated by ca. 400 km (Fig. 1), and the K/Pg boundary horizon itself is not preserved in the Leﬁpán or Salamanca Formations, these Maastrichtian and Danian collections represent broadly similar, marginal marine depositional settings and the only large, stratigraphically constrained leaf collections from their time periods sourced from a single region in the Southern Hemisphere. In addition to the summary presentation and citations that follow, further detailed accounts of collecting methods and sites and full descriptions of the leaf morphotypes are in separate preparation. Leﬁpán Formation.—The siliciclastic Leﬁpán Formation conformably overlies the Campanian–Maastrichtian ﬂuvio-estuarine Paso del Sapo Formation, and it is unconformably overlain by the Eocene Barda Colorada Ignimbrite (Spalletti 1996; Aragón and Mazzoni 1997; Scasso et al. 2012; Aragón et al. 2018) and other Paleogene volcanic units (Aragón et al. 2018). Deposited in the shallow, paleo-Atlantic Paso del Sapo embayment (Fig. 1A,B), the Leﬁpán Formation records the latest Cretaceous (?Campanian–Maastrichtian) to early Paleocene (Danian) inﬁlling of the Jurassic– early Paleocene Cañadón Asfalto Basin (Fig. 1A) (Spalletti 1996; Scasso et al. 2012; Figari et al. 2015). Leaf cuticular pCO2 estimates (Martínez et al. 2018), TEX86 proxy records (Scasso et al. 2012; Vellekoop et al. 2017), and Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 4 ELENA STILES ET AL. Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION paleobotanical evidence (Baldoni 1992; Baldoni et al. 1993; Barreda et al. 2012; Wilf et al. 2017) indicate that the upper Maastrichtian Leﬁpán Formation was deposited in mesothermal (or warmer), frost-free climates (Fig. 1A) along a coastline fringed by patchy woodlands and mangroves; macrofossil evidence suggests areas of rain forest as well (Wilf et al. 2017; Escapa et al. 2018). The San Ramón Section (SRS; Fig. 1B,D) studied here is the most complete of the Leﬁpán Formation (Scasso et al. 2012), comprising marginal, tidal-ﬂat deposits to fully marine sediments within a tidally dominated deltaic setting that ranges from ?Campanian– Maastrichtian to Danian in age (Legarreta and Uliana 1994; Spalletti 1996; Barreda et al. 2012; Scasso et al. 2012; Vellekoop et al. 2017; Butler et al. 2019). The K/Pg impact layer recognized at other sites around the world (e.g., Alvarez et al. 1980, 1990; Orth et al. 1981; Brooks et al. 1986; Lerbekmo and St. Louis 1986; Schulte et al. 2010) is not preserved in the SRS, probably due to bioturbation or erosion at that particular level (Scasso et al. 2012). However, the K/Pg in the Leﬁpán Formation is constrained to about 4 m of section based on biostratigraphic data, including the marker Turritella malaspina lag bed as the ﬁrst Danian deposit (Fig. 1D) (Medina and Camacho 1990; Scasso et al. 2012), dinoﬂagellate index taxa (Barreda et al. 2012; Vellekoop et al. 2017), age-diagnostic continental palynomorphs (Barreda et al. 2012), and a sudden and signiﬁcant turnover of invertebrate faunas (Aberhan and Kiessling 2014) and microﬂoras 5 with the extinction of ca. 10% of total and 50% of angiosperm palynotaxa (Fig. 1D) (Barreda et al. 2012). Leﬁpán Formation specimens analyzed here were collected in the SRS (Fig. 1A,C,D) in sandstone–mudstone tidal-ﬂat deposits (Scasso et al. 2012). Localities LefW, LefE, and LefL, as detailed in Donovan et al. (2016, 2018) and Wilf et al. (2017), yielded a total of 1062 dicot-leaf specimens from unbiased collections biostratigraphically constrained to the 67–66 Ma range and most likely in the 66.5–66.0 range based on dinoﬂagellate markers (Fig. 1D) (Barreda et al. 2012; Scasso et al. 2012; Vellekoop et al. 2017). All identiﬁable material was collected at these sites and taken back to the MEF, where it was vetted and censused (no identiﬁable fossils were discarded in the ﬁeld). The LefW macroﬂoral site corresponds to the same plant-bearing beds discussed in Scasso et al. (2012) and Vellekoop et al. (2017). The LefW collection (Supplementary Table 3) includes 278 dicot-leaf specimens spanning about 20 m of stratigraphic section from four collecting horizons, the youngest of which is located 5 m below the Danian Turritella marker bed (Scasso et al. 2012; Donovan et al. 2016; Vellekoop et al. 2017). Approximately 1000 m map distance east of LefW is the single fossiliferous horizon yielding the macroﬂoras of the LefE and LefL collections. Locality LefE, 21.5 m below the Turritella marker bed, is closest to LefW. The LefE quarry extends about 40 m along the horizon (Wilf et al. 2017), from where 614 dicot-leaf fossils were collected. LefL is located approximately FIGURE 1. Setting of paleobotanical localities. A, Paleogeographic reconstruction of Patagonia at K/Pg time, redrawn from Scasso et al. (2012). Light blue diagonal pattern: shallow platform; yellow horizontal pattern: coastal lowlands; dashed line: approximate boundary between paleoclimatic belts as inferred by Scasso et al. (2012). Locations of panels B and C marked. B, Location of Scasso et al.’s (2012) San Ramón section (within star) of the Leﬁpán Fm., containing Maastrichtian macroﬂoras and Maastrichtian and Danian palynoﬂoras. Modiﬁed after Barreda et al. (2012). C, Locations of Danian paleobotanical sites: Palacio de los Loros (PL), Salamanca Fm.; Las Flores (LF), Peñas Coloradas Fm.; and Bosque Petriﬁcado José Ormachea (OR, Salamanca Fm., used here for pollen data only). Modiﬁed after Clyde et al. (2014) and Comer et al. (2015). D, Summary stratigraphy showing chronostratigraphic and absolute age constraints, placement of palynological (tick marks) and macroﬂoral sampling sites (black stars; compiled from Iglesias 2007; Barreda et al. 2012; Clyde et al. 2014; Comer et al. 2015; Donovan et al. 2016, 2018). Summary of absolute ages of the fossil sites (see text for details): Leﬁpán ﬂoras, 67–66 Ma, most likely 66.5–66.0 Ma; PL1 ﬂora, 66.4–65.7 Ma (C29n); PL2 ﬂora, 64.7–63.5 Ma (C28n); LF ﬂora, 62.5– 62.2 Ma (C27n). Range of stratigraphic section comprising approximate locations of LefW sampling horizons (as described in Vellekoop et al. 2017) indicated by dashed line (see “Materials” for details). LefE, LefL, and LefW are shown on a single column for simplicity but represent different locations (see text for details). LefE and LefL come from a single laterally extensive horizon that varies in stratigraphic distance below the Turritella bed. The position shown is for LefL. BBF, Bajo Barreal Fm. (Color online.) Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 6 ELENA STILES ET AL. 500 m (map distance) east of LefE, in the same bed, at 24 m locally below the Turritella bed (Donovan et al. 2016) and yielded 170 dicot-leaf specimens. The single fossiliferous horizon containing LefE and LefL cannot be correlated precisely to those in LefW due to cover and erosion in the intervening landscape, but their ages are probably very similar based on stratigraphic position. Salamanca and Peñas Coloradas Formations.— The Danian Salamanca and Peñas Coloradas Formations are the oldest Cenozoic sedimentary units in the north-central San Jorge Basin (Fig. 1A) (Sylwan 2001; Clyde et al. 2014; Comer et al. 2015). In our study area (Fig. 1A, C), tidally inﬂuenced, marginal to estuarine deposits of the early Danian Salamanca Formation (Legarreta and Uliana 1994; Iglesias 2007; Comer et al. 2015) unconformably overlie ﬂuvial and pyroclastic deposits of the Late Cretaceous (Campanian) Bajo Barreal Formation or (where preserved) the Maastrichtian La Angostura Basalt (Fig. 1D) (Iglesias 2007; Clyde et al. 2014; Comer et al. 2015), and they are unconformably overlain by the ﬂuviovolcanic deposits of the late Danian Peñas Coloradas Formation of the continental Rio Chico Group (Fig. 1C,D) (Iglesias 2007; Raigenborn et al. 2010; Clyde et al. 2014; Comer et al. 2015; Krause et al. 2017). At the Las Flores (LF; Fig 1C) Peñas Coloradas Formation locality, deposits overlie the Maastrichtian Colhué Huapi Formation and La Angostura Basalt (Casal et al. 2015; Comer et al. 2015). Fossil occurrences from the Salamanca and overlying Peñas Coloradas Formations are consistent with humid, mesothermal, frost-free climates (Bonaparte et al. 1993; Brea et al. 2005; Iglesias et al. 2007; Palazzesi and Barreda 2007; Raigemborn et al. 2009; Futey et al. 2012; Clyde et al. 2014; Ruiz et al. 2017, 2020). Palynoﬂoras of the Salamanca Formation and related strata over larger areas reﬂect a range of environments, from mangrove swamps to lowland and upland forests (Petriella and Archangelsky 1975; Zamaloa and Andreis 1995; Volkheimer et al. 2007). In the study area (Fig. 1C, D), local pollen records show diverse, angiosperm-dominated lowland forests (Petriella and Archangelsky 1975; Clyde et al. 2014). The unbiased, lab-vetted (the same collecting and tallying methods used as for the Leﬁpán ﬂoras) early Paleocene leaf collections analyzed in this study came from two early Danian Salamanca Formation localities in the Palacio de los Loros sampling area (PL1 and PL2) and one late Danian locality in the Peñas Coloradas Formation, the LF plant-fossil site (Fig. 1B) (Iglesias 2007; Iglesias et al. 2007; Clyde et al. 2014). Biostratigraphic data from foraminifera, dinoﬂagellates, and calcareous nannoplankton indicate the early Danian age for the local Salamanca Formation, with a maximum absolute age of 67.31 ± 0.55 Ma from 40Ar/39Ar dating of the La Angostura Basalt ﬂow underlying the formation in the easternmost exposures of the study area (Fig. 1D) (Clyde et al. 2014). The U-Pb age of a tuff layer in the Peñas Coloradas Formation at Palacio de los Loros is 61.984 ± 0.041 Ma, placing it in the late Danian (Fig. 1D) (Clyde et al. 2014). Combined analysis of paleomagnetic stratigraphy, biostratigraphy, and U-Pb and 40Ar-39Ar ages place the paleobotanical sites PL1, PL2, and LF within geomagnetic polarity chrons C29n (65.58–64.88 Ma), C28n (64.67–63.49 Ma), and C27n (62.52– 62.22 Ma), respectively (Fig. 1D) (Clyde et al. 2014; Comer et al. 2015), using the 2012 Geologic Time Scale (Gradstein et al. 2012). Between the early Danian Salamanca and late Danian Peñas Coloradas Formations, there is a sharp change in the depositional environment. The strata at PL1 and PL2 were deposited in marginal estuarine settings, whereas LF was deposited in a nearly fully terrestrial ﬂuvio-volcanic environment (Comer et al. 2015). Locality PL1 (Fig. 1A,C,D) produced 1089 dicot-leaf specimens, preserved in sand–siltstone sediments interpreted as lateral accretion beds of abandoned tidal channel ﬁll (facies Sab in Comer et al. 2015). The younger locality PL2 yielded 1132 dicot-leaf specimens, collected from silty claystones interpreted as the transitional facies of tidal ﬂats prograding over a coastal plain (facies SCt in Comer et al. 2015). Sediments in locality LF are the coarsestgrained of the Danian macroﬂoral sites, from where 564 dicot-leaf specimens were recovered from poorly sorted litharenites interpreted as channel ﬁlls (facies LF1 in Comer et al. 2015). Based on sedimentology and preservational Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION quality, the potential order of transport distances for fossil leaves is ranked highest to lowest as LF, PL1, and PL2. Donovan et al. (2018) noted that preservation quality in Salamanca Formation locality PL1 is similar to that of the Leﬁpán Formation, indicating minimal preservation bias between the oldest Paleogene locality and the Maastrichtian collections in this study. Analytical Methods Macroﬂoral turnover across the K/Pg transition was addressed through analyses of (1) change in species composition, (2) morphospace shifts among assemblages, and (3) the potential biasing effect of the ca. 400 km separation between the Cretaceous and Paleogene collection sites using crosschecks from local pollen records in both formations (Fig. 1D). Preliminary Leﬁpán Formation morphotypes (Donovan et al. 2016) were signiﬁcantly revised and updated based on leaf architectural characters (Ellis et al. 2009). Danian morphotypes of the Salamanca and Peñas Coloradas Formations are based on the morphotype set of the PL1, PL2, and LF macroﬂoral localities (Iglesias 2007; Iglesias et al. 2007) and an additional set published in the supplementary information of Donovan et al. (2016; Supplementary Table 4). A total of 58 Maastrichtian and 43 Danian morphotypes were established and used in the subsequent analyses (Supplementary Table 4). Each morphotype is here interpreted as likely to have been produced by a single species with morphologically distinct leaves and will be referred to as a species throughout this study. An updated specimenlevel collections inventory of all leaf morphotypes as used here is archived in Supplementary Table 3. Extinction and Turnover.—All Maastrichtian and Danian collections were grouped into two respective assemblages for macroﬂoral extinction estimates and morphospace analyses due to their self-similar ﬂoral compositions and morphospace occupation, based on preliminary analyses. Each of the Maastrichtian morphotypes was compared with the Danian morphotypes in search of K/Pg survivor pairs based on a detailed comparison of their leaf 7 architecture (per Johnson et al. 1989; Ash et al. 1999; Ellis et al. 2009). Maastrichtian and Danian morphotypes that shared all morphological characters or that fell within each other’s ranges of variation were considered survivor pairs. Once the survivor pairs were established, they were each considered as a single species, along with all the other leaf species, in a principal components analysis (PCA) applied to a matrix of species abundances per sample, with the objective of testing compositional heterogeneity among the considered Maastrichtian and Danian macroﬂoral collections. In this analysis, Maastrichtian collections LefW and LefE+LefL were considered as two samples, because LefW was collected along several horizons within the same small canyon (see “Materials”), and LefE and LefL were collected along the same fossiliferous horizon. For rareﬁed (Tipper 1979) species richness analysis across the K/Pg, the Maastrichtian LefE and LefL sites were grouped into a single sample, from which LefW was excluded because it includes specimens from multiple horizons with uncertain stratigraphic relationships to horizon LefE+LefL. The Salamanca (PL1 and PL2) and Peñas Coloradas (LF) localities (Fig. 1A,C,D) (Iglesias 2007; Iglesias et al. 2007) were considered for rarefaction individually because they span three Danian time intervals (Fig. 1D) (see “Materials”; Clyde et al. 2014; Comer et al. 2015). Each rarefaction curve was plotted with a 95% conﬁdence interval using the R package iNext (Hsieh et al. 2016). As a baseline for comparison of rareﬁed species richness between Patagonian and North American K/Pg assemblages, three representative dicot-leaf samples surpassing 350 specimens each (per Burnham 1993) from meter-binned collections of the Maastrichtian Hell Creek and Danian Fort Union Formations in the WB of southwestern North Dakota were selected from the dataset of Wilf and Johnson (2004; see also Johnson 2002). The Dean Street level found 15 m below the K/Pg boundary (Wilf and Johnson 2004) represents the most diverse, latest Maastrichtian HCIII zone (Johnson 2002). Two representative Fort Union Formation collection horizons were based on specimen counts >350 and Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 8 ELENA STILES ET AL. magnetostratigraphic constraints. Horizon +7 m is the most specimen-rich representative of early Danian Fort Union Formation fossil horizons, corresponding to geomagnetic polarity chron C29r (which is unrecorded in Patagonia). The +38 m horizon is constrained to chron C29n (Hicks et al. 2002; Johnson 2002), serving as a temporal analog to the PL1 locality in Patagonia (Fig. 1D) (Clyde et al. 2014). While acknowledging work on diverse Paleocene ﬂoras from the more southerly Denver and San Juan basins (Johnson and Ellis 2002; Flynn and Peppe 2019; Lyson et al. 2019), we focus on the ﬂoras of the WB for comparison, because they come from similar absolute paleolatitudes to our samples (i.e., ca. 51.3°S for the Danian Patagonian ﬂoras, ca. 48.4°S for the Cretaceous Leﬁpán ﬂoras, and ca. 49.4°N for the WB ﬂoras, versus ca. 42.5°N for the Denver Basin, following Iglesias et al. 2007: ﬁg. 3), contain both Cretaceous and Paleocene ﬂoras that are well sampled in a single area, and remain the best-sampled and described boundary-spanning K/Pg macroﬂoras of NAM. Morphospace Analysis.—Species richness and morphological diversity are not always coupled, and this disconnection may be driven by underlying selective pressures (Foote 1993; Roy and Foote 1997). Morphospace analysis is here used as a quantitative tool to measure morphological diversity and phenotypic relationships among angiosperm leaf species and their change through time, by summarizing morphological characters in a mathematical space where phenotypic dissimilarities are observed as graphical distances (Mitteroecker and Huttegger 2009). Leaf architecture is related both to systematic afﬁnities and environmental parameters (e.g., Wolfe 1995; Wilf 1997; Little et al. 2010; Givnish and Kriebel 2017), making leaves ideal candidates to simultaneously test species and morphological turnover across the K/Pg. Through morphospace analysis, the multivariate relationships among characters can shed light on selective morphological extinction patterns, if present, and the relationships between morphological disparity and species richness. Based on the Manual of Leaf Architecture (Ellis et al. 2009), forty-six discrete shape, size, margin, and venation characters (Supplementary Table 5) were scored for each of the Maastrichtian and Danian morphotypes (Supplementary Table 7). Features that were not preserved (or observable) in at least three-fourths of the specimens, such as fourth- and higher-order venation, were excluded to reduce noise in the dataset. After observation of all available material, character states for each morphotype were usually based on one or two (if a single specimen did not preserve all morphological characters) selected exemplar specimens. If a morphotype showed signiﬁcant variation in one or more characters after observation of all available samples, end members were separated in the morphological matrix designated by letters following the morphotype name (e.g., SA9A, SA9B; Supplementary Table 7) to ensure that all morphological diversity was captured in the subsequent ordination. Maximum size was based on the largest specimen of each species in the collection. Missing characters were coded as “NA.” The morphological matrix (Supplementary Table 7) was ordinated using principal coordinates analysis (PCoA) with the R Package ape (Paradis and Schliep 2018). Because it compares each morphotype on a character-by-character basis, PCoA is considered the best-performing method for datasets with uneven preservation and missing characters (Foote 1994; Roy and Foote 1997). The percentages of missing data for each character and each morphotype are reported in Supplementary Table 8. To understand how species are distributed in space and to explore possible character-related patterns, the same scores obtained in the PCoA ordination were analyzed by graphically superimposing character states on plotted scores including axes PCoA 1–PCoA 3. The process was repeated for each character. To obtain a quantitative measure of morphospace occupation for Maastrichtian and Danian assemblages and to verify consistency in the results, four disparity measures were calculated separately for each Maastrichtian (LefW, LefE, and LefL) and Danian (PL1, PL2, and LF) leaf assemblage and for grouped Maastrichtian (LefW+LefE+LefL) and Danian (PL1 +PL2+LF) assemblages. Based on the ﬁrst four axes of the PCoA, (1) a hypercuboid volume and (2) a sum of ranges were estimated Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION (Foote 1994; Wills et al. 1994). Based on the Euclidean pairwise distance matrices, the (3) average pairwise distance and (4) maximum pairwise distance were extracted. The hypercuboid volume was estimated by multiplying the ranges of the ﬁrst four axes (Wills et al. 1994). Following Gerber’s (2019) proposed measures of disparity for discrete character spaces, the (3) average and (4) maximum pairwise distances of the Euclidean distance matrix are reported here (Supplementary Table 6) for each local assemblage and the grouped Maastrichtian and Danian assemblages. Pollen Analysis and Regional Floral Heterogeneity.—Palynological records from the same formations and sections offer the closest possible points of comparison to macroﬂoras, and they provide, for the most part with taxonomic resolution above the species level, information about changes in regional ﬂoral composition (Behrensmeyer et al. 2000; Nichols and Johnson 2008). To evaluate the effects of the approximately 400 km distance separating the Maastrichtian and Danian localities (Fig. 1A) as a spatial bias affecting macroﬂoral composition, published palynological records for the same two sampling areas and stratigraphic framework (Fig. 1D) (Barreda et al. 2012; Clyde et al. 2014) were compared at taxon-by-taxon and whole-assemblage levels. The Leﬁpán Formation palynological records from the SRS span the boundary (Fig. 1D) (unlike the Leﬁpán macroﬂoras; Barreda et al. 2012); thus, both their Maastrichtian and Danian components were compared with the exclusively Danian records of the Salamanca Formation at Palacio de los Loros and adjacent areas sampled at high stratigraphic resolution (Clyde et al. 2014). We note that several other palynological studies exist of both formations based on other sections (e.g., Archangelsky 1973; Petriella and Archangelsky 1975; Medina and Camacho 1990; Baldoni et al. 1993; Casal et al. 2015), but our goal is to compare palynological data from the same wellconstrained sections as the macroﬂoras addressed here. The ﬁne temporal correlations between the Leﬁpán and Salamanca Formations are not yet established. V. Barreda (Museo Argentino de Ciencias Naturales, Buenos Aires) kindly reviewed the 9 illustrations and species lists in Clyde et al. (2014) to establish equivalencies between palynotaxa (e.g., “Proteaceae sp. A” and “Proteaceae sp. B”) among the Leﬁpán and Salamanca sections, and her vetted species data were used in subsequent analyses (Supplementary Table 2). Sample-level compositional comparisons were based on a presence– absence matrix of palynomorph species and morphotypes (Supplementary Table 2) and processed in the R vegan package (Oksanen et al. 2017). The presence–absence matrix of palynomorph data was transformed using the Beals smoothing method (McCune 1994; Münzbergová and Herben 2004), which accounts for unevenness in ecological sampling by replacing species’ presence data with a probability of occurrence based on co-occurrences in the sample pool. This method was used to reduce the underlying compositional heterogeneity caused by the inherent sampling bias of the fossil record. The samples were then clustered based on their Bray-Curtis pairwise dissimilarity matrix calculated from the Beals-smoothed dataset and linked using Ward’s method algorithm (Oksanen et al. 2017). Results Extinction and Turnover.—We recognize only ﬁve Maastrichtian leaf species as having a corresponding survivor in any Danian assemblage (Figs. 2, 3), indicating a raw dicot macroﬂoral extinction of 92.2%. Using only the oldest Danian assemblage (PL1 locality) yields a 93.3% extinction. Excluding species represented by a single specimen (singletons) reduces the extinction slightly, to 90.6%. The K/Pg survivor pairs based on Maastrichtian (preﬁx LEF) and Danian (preﬁx SA) morphotypes (Supplementary Tables 1,2) are referred to as Survivor Pair (SP) 1 (LEF57-SA20; Fig. 2A–E), SP2 (LEF64-SA35; Fig. 2F–I), SP3 (LEF6-SA19; Fig. 3A–C), SP4 (LEF18-SA08; Fig. 3D–G), and SP5 (LEF55-SA78; Fig. 3H–J). We interpret SP1 (Fig. 2A–E) to have a botanical afﬁnity with the family Cunoniaceae based on its architectural characters including compound leaves (Fig. 2), supported by the welldocumented presence (and earliest global Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 10 ELENA STILES ET AL. Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION macrofossil occurrence) of this family from abundant co-occurring Lacinipetalum spectabilis ﬂowers with in situ pollen (schizomerioid Cunoniaceae; Jud et al. 2018) from PL2 and other Salamanca Formation localities and fossil wood in the Peñas Coloradas Formation (Raigemborn et al. 2009). The afﬁnities of SP2 (Fig. 2F–I) and SP5 (Fig. 3H–J) remain unknown. Following Iglesias et al. (2007), SP3 (Fig. 3A–C) is equivalent to some specimens designated as “Sterculia” acuminataloba Berry 1937 of the family Malvaceae, and SP4 (Fig. 3D–G) belongs to the family Rosaceae based on diagnostic characters including serrated margins with compound teeth and craspedodromous secondary venation. The survivorship of the family Rosaceae is a new contribution of this study, along with Cretaceous macroﬂoral evidence to support the K/Pg survival of Malvaceae and Cunoniaceae, previously known from pollen records in these sections (Barreda et al. 2012; Jud et al. 2018a,b). Laurophyll morphotypes observed in this study provide evidence for the K/Pg survival of the Lauraceae in Patagonia, although we cannot assign any Maastrichtian laurophyll to a deﬁnite Danian species-level equivalent because they lack cuticular preservation for further analysis (e.g., Carpenter et al. 2018). Based on a conservative “lumping” approach, we established four Maastrichtian laurophyll morphotypes based on their having typical lauraceous leaf architectural features (after Hickey and Wolfe 1975). Leﬁpán Formation morphotypes LEF08, LEF24, LEF26, and LEF32 (Supplementary Table 3), coupled with Danian Laurophyllum piatnitzkyi Berry and Laurophyllum chubutensis Berry of the Salamanca and Peñas Coloradas Formations (Iglesias et al. 2007), add Lauraceae to the list of Patagonian K/Pg macroﬂoral survivor families. Laurophyllum piatnitzkyi is notable as the most abundant 11 species in the Danian assemblages, accounting for ca. 17% of total leaf specimens (Iglesias et al. 2007). The loss of common taxa followed by the emergence of previously rare taxa is a commonly observed pattern across mass extinction intervals (e.g., Erwin 2002; Johnson 2002; Jablonski 2005). A comparable pattern occurs in our survivor pairs (Fig. 4). SP1 of the Cunoniaceae (Fig. 2A–E) is a major component of Maastrichtian ﬂoras, but its abundance is greatly reduced at earliest Danian PL1 before partially recovering in PL2 (Fig. 4). In contrast, Malvaceae SP3 (Fig. 3A–C) and Rosaceae SP4 (Fig. 3D–G), both minor components in Maastrichtian assemblages, surpass 5% of assemblage composition at early Danian PL1 and are reduced back to minor components at PL2 and LF (Fig. 4). Leaf morphotypes SP2 and SP5, of unknown afﬁnities, remain minor components throughout. Rareﬁed dicot-leaf richness dropped in Patagonia by almost 40% across the K/Pg and remained comparably low from the early to late Danian (Fig. 5). Patagonian Danian ﬂoras are remarkably homogeneous across time and facies, from early to late Danian and from marginal marine to pyroclastic–ﬂuvial environments, in comparison with the relatively more heterogeneous Leﬁpán ﬂoras deposited in similar facies and spanning a narrower time interval (Fig. 6). A sharp drop in rareﬁed species richness was also observed in the North American K/Pg ﬂoras of the WB in North Dakota (e.g., Johnson 2002; Wilf and Johnson 2004). However, our rarefaction also shows that Patagonian ﬂoras are signiﬁcantly more diverse than the North Dakota ﬂoras not only during the early Danian (Iglesias et al. 2007) but also the Maastrichtian (Fig. 5). Morphospace Analysis.—Pre- and post-K/Pg leaf assemblages signiﬁcantly overlap in FIGURE 2. K/Pg survivor pairs (SPs) from the Maastrichtian Leﬁpán (blue circles) and Danian (unmarked) Salamanca and Peñas Coloradas Formations (see also Fig. 3). A–E, SP1, Cunoniaceae, including articulated compound leaf. Note ovate and asymmetrical blades of variable leaﬂets, curved primary vein, craspedodromous secondary venation, mixed percurrent tertiaries perpendicular to secondaries, and small triangular teeth with long-rounded sinuses. A, MPEF-Pb-4416 from locality LefE; B, MPEF-Pb-4349, LefE; C, MPEF-Pb-9154 from locality PL2; D, MPEF-Pb-3691, PL1; E, MPEF-Pb-3694, PL1. F–I, SP2. Note well-developed palmate lobing, toothed margin, straight secondaries with opposite insertion, compound agrophic veins, and alternate percurrent tertiaries. F, MPEF-Pb-3701a, LefL; G, MPEF-Pb-2031, PL1; H, MPEF-Pb-3701b detail of alternate percurrent venation; I, MPEF-Pb-2031 (also H) detail of alternate percurrent venation. (Color online.) Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 12 ELENA STILES ET AL. Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION 13 FIGURE 3. K/Pg survivor pairs (SPs; continued from Fig. 2) from the Maastrichtian Leﬁpán (blue circles) and Danian (unmarked) Salamanca and Peñas Coloradas Fms. A–C, SP3, “Sterculia” acuminataloba. Note the palmately lobed form with entire margins, three strong primary veins, central primary deﬂected by strong basal secondaries, interior secondaries, intersecondary veins, agrophic veins, irregularly branching brochidodromous secondaries with spacing decreasing apically, and percurrent tertiaries nearly perpendicular to the primary vein. A, MPEF-Pb-4662a from locality LefW; B, MPEF-Pb-3692, PL1; C, MPEF-Pb-3695, PL2. D–G, SP4, Rosaceae similar to Crataegus spp. Note ovate shape, craspedodromous secondaries, pinnate lobing with toothed lobes, large triangular teeth, opposite to subopposite secondaries. D, MPEF-Pb-4487, LefE; E, MPEF-Pb-4482, LefE; F, MPEF-Pb-3693, PL1; G, MPEF-Pb-4030, PL1. H–J, SP5. Note ovate-elliptic leaf shape, opposite to subopposite concave-upward brochidodromous secondaries, intersecondary veins perpendicular to primary, widely spaced irregularly angled tertiaries ranging from opposite to alternate percurrent, and ﬁmbrial vein running along entire margin. H, MPEF-Pb-4870, LefL; I, MPEF-Pb-4835, LefE; J, MPEF-Pb-3019, LF. (Color online.) morphospace, but there is an increase in morphospace occupation between the terminal Cretaceous and early Paleogene (Fig. 7). This result shows no signiﬁcant loss of characters and higher morphological disparity in postcompared with pre-K/Pg assemblages, despite lower species richness in the Danian. Morphospace occupation across the K/Pg is characterized by three notable shifts. First, morphospace volume expands, driven by Danian lobed species displaying blade incision characters absent in the Maastrichtian. Examples include lobed species with toothed margins such as SA35 (see circled groups in Fig. 8A). Second, within the morphospace area shared by Maastrichtian–Danian assemblages (Fig. 8), more Danian species have lobed blades, toothed margins, and craspedodromous venation. FIGURE 4. Relative abundance of each survivor pair (SP; see Figs. 2, 3) in total leaf counts from Maastrichtian and Danian ﬂoral assemblages. Third, extremes in morphological variation, seen as end members along the PCoA axes, are all represented by Danian species, signaling higher morphological disparity in post-K/Pg assemblages (Fig. 8). For example, with the lowest score along axis PCoA 1, Danian species SA35 (Fig. 8A, lower left) is lobed with craspedodromous secondary veins and toothed margins, whereas SA50 (Fig. 8B, upper right), with the highest score for axis PCoA 1, is unlobed with entire margins and FIGURE 5. Rareﬁed leaf species richness with 95% conﬁdence intervals for Patagonian sites (solid lines, this study) and Williston Basin, North Dakota (dashed lines, denoted with meters below or above K/Pg impact layer; data from Wilf and Johnson 2004). Data include all Maastrichtian (black) and Danian (gray) dicot-leaf samples, including singleton species (see “Methods” for details). Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 14 ELENA STILES ET AL. FIGURE 6. Compositional differences between Maastrichtian (K) and Danian (Pg) assemblages based on a species by abundances principal components analysis (PCA), showing increased similarity of ﬂoral composition from the Maastrichtian (Lef) to the Danian (PL, LF) macroﬂoras, even though the Danian assemblages represent a longer time interval and a much greater array of facies types. PCA 1 variance explained = 72.7%, PCA 2 variance explained = 11.5%. brochidodromous venation. Intermediate morphotypes along PCoA 1 display combinations of entire and toothed-margined characters and additional, less common venation types. Maastrichtian morphotypes cluster toward the higher scores of PCoA 1 and most share morphological characteristics with SA50, such as entire margins, no lobes, and brochidodromous secondaries (Fig. 8). When we analyzed morphospace occupation by character states (Supplementary Table 5), the most signiﬁcant observable variation was found in characters of maximum blade size, lobation, and margin types. Maximum leaf size ranges from nanophyll to megaphyll, with representatives of both Maastrichtian and Danian species in each size class. The representation of both Maastrichtian and Danian leaves within the same size class range could indicate isotaphonomic leaf assemblages. However, for purposes of morphospace analysis, leaves in the smallest (nanophyll) and largest (macrophyll and megaphyll) size classes were excluded, because they included too few specimens to produce an interpretable morphospace occupation pattern. Individually plotting the ordination scores by maximum leaf size classes of each species (Fig. 9), we found that shifts in morphospace occupation across the K/Pg become more signiﬁcant as maximum leaf size increases (Figs. 7, 9). Within each size class, there appear to be distinct morphological trends (Fig. 9). In the FIGURE 7. Percentage increase in leaf morphospace occupation from Maastrichtian to Danian in Patagonia based on four measures of disparity (see “Methods” for details). A, Morphospace volume increase based on all Maastrichtian and Danian species. B, Morphospace area change partitioned by most common leaf size classes. Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION 15 FIGURE 8. Morphospace occupation of Maastrichtian and Danian assemblages from principal coordinates analysis (PCoA). The expanded Danian morphospace (see Fig. 7) indicates higher morphological diversity in post-K/Pg ﬂoras despite lower species richness. A, Axis 2 vs. axis 1. Characteristically lobed outliers driving Danian morphospace expansion are recognized as two groups as circled; labeled exemplar species are: 1, SA35; 2, SA39; 3, SA55; 4, SA19A; 5, SA19B. B, Axis 3 vs. axis 1. Morphological end members along PCoA 1, both Danian, labeled: 1, SA35; 2, SA50. smallest size classes, microphylls and notophylls, Maastrichtian leaves occupy a larger morphospace than Danian species, as shown by the four end members along axes 1 and 2 (Fig. 9A, labeled 1–4; Fig. 9B, labeled 1, 2, and 4). This result is supported by a reduction in morphospace volume (Fig. 7B), indicating that leaves in these size classes are more morphologically diverse in Maastrichtian assemblages. In contrast, the larger mesophyll-sized leaves (Fig. 9C) expand in morphospace occupation after the K/Pg (Fig. 7B). Danian mesophylls span a wide range of morphologically diverse lobed, unlobed, entire-margined, and toothed morphotypes. Mesophyll Maastrichtian morphotypes are generally entire-margined and share self-similar secondary venation patterns (e.g., labels 5 and 6, Fig. 9C). We found distinct morphospaces occupied by lobed versus unlobed species, whether we included all species (Fig. 10A), Maastrichtianonly (Fig. 10B), or Danian-only (Fig. 10C) assemblages. Lobed leaves are consistently more morphologically disparate than unlobed types (Fig. 10B,C), a notable result considering that presence of lobes is only one of the more than 40 characters weighted equally in the ordination. Lobation in Danian species is generally associated with non-entire margins and craspedodromous venation, a relatively uncommon combination in Maastrichtian assemblages. Regarding margin characters, in both Maastrichtian and Danian assemblages, toothed and entire-margined morphotypes occupy distinct morphospaces (Fig. 10D), presumably in large part a result of the numerous characters in the matrix that pertain to toothed margins that are coded as zeroes for entire-margined morphotypes. However, there is some overlap among toothed and entire-margined types in Maastrichtian assemblages, characterized by species with margins scored as crenate and a few entire-margined examples (Fig. 10E). Interestingly, there is no such overlap in Danian assemblages (Fig. 10F), graphically showing the loss of crenate margins from pre- to post-K/Pg assemblages and indicating one of the few morphological losses. Pollen Analysis and Floral Heterogeneity among Sections.—Comparison of published pollen records from the same sections as the macroﬂoral localities (Fig. 1D) shows that the Maastrichtian–Danian Leﬁpán and Danian-only Salamanca Formation samples (Fig. 1A) share most of the same pollen species and thus the same higher taxa (families and possibly genera), whether or not the Maastrichtian pollen data are included. First, in the closest Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 16 ELENA STILES ET AL. (Supplementary Table 2). Second, the Salamanca Formation also shares about 75% of palynospecies with the Danian strata of the Leﬁpán (Barreda et al. 2012; Supplementary Table 2). Thus, the same higher plant taxa are inferred to be present in the Danian microﬂoras of both formations (Fig. 1), despite the high species-level turnover indicated by leaves. Third, the percentage of shared palynotaxa among the Maastrichtian Leﬁpán and the Danian Salamanca (i.e., the pollen analog to the macroﬂoras studied here; Fig. 1) is similar to that among Maastrichtian and Danian Leﬁpán Formation samples within the SRS. These palynological results all suggest that geographic separation does not signiﬁcantly inﬂuence the composition of higher taxa between the two localities, supporting the comparability of the Maastrichtian and Danian macroﬂoras undertaken here. Considering all the Danian palynotaxa (Leﬁpán and Salamanca), 80% are Cretaceous–Paleogene survivors based on the Cretaceous Leﬁpán as the source of survivors for both formations, demonstrating the persistence of taxa including the gymnosperm families Podocarpaceae and Classopollis sp. (Cheirolepidiaceae) and the angiosperm families Arecaceae, Liliaceae, Proteaceae, Symplocaceae, and Gunneraceae, as well as various bryophytes and ferns (Supplementary Tables 1, 2). Cluster analysis of the Beals smoothed compositional matrix (Fig. 11) shows that despite the high percentage of palynomorph species shared between the two formations, compositional differences associated with age and formation can be recognized. Discussion FIGURE 9. Morphospace occupation (axis 2 vs. axis 1) partitioned by maximum leaf size per species using the same PCoA scores for each species shown in Fig. 8. Microphyll is the smallest size class present; mesophyll is the largest. A, Microphylls, selected end-member morphotypes with icons are 1, LEF16; 2, LEF20; 3, LEF46; 4, LEF34. B, Notophylls, examples are 1, LEF64; 2, LEF01; 3, SA50; 4, LEF05. C, Mesophylls, examples are 1, SA35; 2, SA74; 3, LEF12; 4, SA73; 5, LEF07; 6, LEF26; 7, SA55. stratigraphic comparison with the leaf data, approximately 60% of palynospecies in the Danian Salamanca Formation are shared with the Maastrichtian part of the Leﬁpán Formation A high angiosperm macroﬂoral extinction percentage, drop in rareﬁed species richness, depauperate and homogeneous early Paleocene ﬂoras (Fig. 6) despite spanning a range of continental to marginal facies (e.g., Comer et al. 2015), and signiﬁcant extinction of specialized plant–insect associations in Patagonia (Donovan et al. 2016) all provide evidence of a signiﬁcant K/Pg ﬂoral extinction event as seen in NAM (Fig. 5) (Wolfe and Upchurch 1986; Johnson and Hickey 1990; Johnson 2002; Wilf and Johnson 2004). Our results support a Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION 17 FIGURE 10. Principal coordinates analysis (PCoA axis 2 vs. axis 1) coded by time period, lobed vs. unlobed species (A–C), and toothed vs. entire-margined species (D–F). Species ordination scores are the same as and extracted from the analysis shown in Fig. 8. A–C, Lobed species lead the morphospace increase from Maastrichtian to Danian assemblages. D–F, Toothed and entire-margined species occupy distinct areas of morphospace in all assemblages and increase in separation in Danian assemblages, indicating a loss of intermediate morphospace across the extinction interval. First column shows morphospace occupation by all species, colored by respective character. Second column shows morphospace distribution of Maastrichtian species only. Exemplars in B, 1, LEF64; 2, LEF66; 3, LEF46; 4, LEF05; and E, 1, LEF64; 2, LEF53; 3, LEF7; 4, LEF46. Third column shows morphospace distribution of Danian species only. Exemplars in C, 1, SA35; 2, SA48; 3, SA50; 4, SA39; and F, 1, SA35; 2, SA50. disruption in plant communities of global extent across the K/Pg (Vajda et al. 2001; Nichols and Johnson 2008; Barreda et al. 2012; Cantrill and Poole 2012; Vajda and Bercovici 2014; Donovan et al. 2016). Lauraceae have recently been proposed as the principal component of K/Pg recovery macroﬂoras alongside the classic fern spike in the North American Ratón Basin (Berry 2019), although Lauraceae are not reported from the well-sampled early Danian localities in North Dakota (Johnson 2002). The dominance of L. piatnitzkyi in early Paleocene Patagonian macroﬂoras, and of several other leaf morphotypes assigned to the family (Iglesias 2007; Iglesias et al. 2007) would be consistent with the presence of Lauraceae-dominated K/Pg recovery ﬂoras in regions of both North and South America. Despite the similarities between Patagonian and North American records, the subtle differences between them suggest that extinction could have been heterogeneous between the two regions. Morphological turnover shows interesting differences between the WB and Patagonia, even though the WB ﬂoras have not been analyzed in morphospace. Maastrichtian assemblages of North Dakota are characterized by the abundance of leaves with a “Cretaceous look” or unusual lobation (Johnson 2002: p. 371), a feature that is drastically reduced in the early Paleocene (Johnson and Hickey 1990; Johnson 2002). In contrast, the increase in proportion of lobed and toothed species in the early Paleocene of Patagonia (Fig. 8) (Iglesias et al. 2007) leads to an expansion in morphospace occupation by post-K/Pg assemblages. Despite our estimate of almost complete species-level macroﬂoral turnover in Patagonia, the continuity and expansion of leaf morphologies (Fig. 8) and, presumably, their underlying ecological and phylogenetic diversity across the K/Pg could, in part, reﬂect low turnover at higher taxonomic levels observed in both the microﬂoral and macroﬂoral records of Patagonia (Barreda et al. 2012; Supplementary Table 1). Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 18 ELENA STILES ET AL. FIGURE 11. Cluster analyses of palynospecies occurrences with Beals smoothing (see “Methods” and Fig. 1) from the Maastrichtian (samples M1–3) and Danian (D1–11) Leﬁpán Fm. (Barreda et al. 2012) and Danian-only Salamanca Fm. (remaining samples; Fig. 1) (Clyde et al. 2014). A, All species. B, Gymnosperms and angiosperms only. C, Angiosperms only. Both WB and Patagonian species richness suffer a sharp drop between Maastrichtian and Danian assemblages (Fig. 5). The K/Pg drop in rareﬁed species richness, though severe in both areas, is much sharper in the WB (ca. 75%) than in Patagonia (ca. 45%; Fig. 5). Rarefaction highlights another important contrast between the WB and Patagonian records; not only Danian (Iglesias et al. 2007) but also Maastrichtian assemblages in Patagonia are signiﬁcantly more diverse than coeval macroﬂoras in the WB. The Leﬁpán ﬂoras are approximately 40% richer than the most diverse Maastrichtian Hell Creek (HCIII) NAM zone assemblage (Fig. 5). Thus, whereas previous studies of the Danian Salamanca Formation (Iglesias 2007; Iglesias et al. 2007) and Eocene macroﬂoras of Patagonia (Wilf et al. 2003a, 2005) provided evidence for an ancient history of high South American Cenozoic ﬂoral diversity, our results (Fig. 5) extend that history into the Late Cretaceous. The high species richness of Patagonian Paleocene and Eocene assemblages compared with NAM equivalents has been hypothesized in part to be the legacy of low K/Pg ﬂoral extinction as observed in the palynological record (Barreda et al. 2012). Our results suggest that the rich Cenozoic macroﬂoras of Patagonia also carry a legacy of rich Cretaceous ﬂoras, as well as signiﬁcantly earlier recovery of Paleocene species richness resulting from the persistence of most higher taxonomic levels (Supplementary Tables 1, 2). Nonetheless, an emerging body of research shows that ﬂoral diversity in the early Paleocene of the Denver and San Juan Basins can be higher relative to the more northerly WB (Johnson and Ellis 2002; Flynn and Peppe 2019; Lyson et al. 2019). These studies show heterogeneity in NAM ﬂoral richness during the early Paleocene, a pattern warranting further intensive study. Insect damage-type data on the same leaf collections studied here showed a similar pattern of high extinction and robust early recovery compared with NAM (Donovan et al. 2016, 2018). Donovan et al. (2016, 2018) posed the disappearance of plant hosts across the K/ Pg as a potential driving mechanism for the severe insect herbivore extinction observed in Patagonia; host-specialized insects such as leaf miners would have been severely affected by an elevated species-level ﬂoral extinction (as in NAM: Labandeira et al. 2002; Donovan et al. 2014). Our results conﬁrm this interpretation and suggest that despite the low K/Pg turnover of major clades observed in ﬂoras of Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION Patagonia and elsewhere (see Sauquet and Magallón 2018), high plant-species turnover resulted in devastating consequences for terrestrial faunas. The empirical species-extinction percentage of >90% in Patagonia in all likelihood is positively biased by several factors, including coarser stratigraphic sampling than in WB macroﬂoras, geographic variation, and climatic effects, and that is why we present it as a maximum estimate. Regarding sampling, the uncertain temporal placement of the Leﬁpán Formation macroﬂoras within the last ca. million years before the K/Pg boundary (Barreda et al. 2012; Vellekoop et al. 2017) and the lack of earliest Danian (chron 29r) sediments preserved in the Salamanca Formation probably bias against ﬁnding a higher number of survivor pairs (Fig. 1). The limited stratigraphic coverage of macroﬂoras in the upper Leﬁpán Formation is analogous to considering only a small interval of the Hell Creek Formation (Johnson et al. 1989; Johnson 2002; Wilf and Johnson 2004), where there is a general trend of lower percentages of observed survivor dicot-leaf species in a simple experiment where the distance of sample windows below the boundary layer increases (Fig. 12). Furthermore, observed extinction may exceed 90% even for some intervals relatively close to the boundary, as can be seen in the 20–30 m and 40–50 m bins of the Hell Creek Formation (Fig. 12). Although there are macroﬂoral collections from lower Leﬁpán Formation strata (Andruchow-Colombo et al. 2018; Martínez et al. 2018), their precise age is not known, and the preserved diversity of dicot leaves is not nearly so extensive as in the upper Leﬁpán studied here. Therefore, observations across a wide stratigraphic range in the Leﬁpán Formation are not possible at this time. Addressing the geographic separation between the Maastrichtian and Danian macroﬂoras (Fig. 1), the cluster results showing differences between the Leﬁpán and Salamanca sections’ microﬂoral assemblages (Fig. 11) provide evidence for some geographical heterogeneity of higher-taxa associations, which would accentuate species-level contrasts observed in the respective macroﬂoras (Behrensmeyer et al. 2000; Nichols and Johnson 2008). Different 19 FIGURE 12. Simulated percentage of K/Pg-surviving Cretaceous dicot-leaf species in the Williston Basin of North Dakota by 10 m bin window below the K/Pg impact horizon (data from Wilf and Johnson [2004], including singletons; see “Discussion” for details). The Leﬁpán leaf ﬂoras studied here, with a 91% observed extinction, could correlate temporally to any one of these stratigraphic bins. underlying palynospecies associations suggest that the 400 km spatial separation of Maastrichtian and Danian assemblages plays some role in the likely overestimation of Patagonian macroﬂoral extinction by imparting a geographical bias (Fig. 11). On the other hand, geographic effects could not have been severe, because the number of shared palynospecies in the same strata as the leaf ﬂoras was very high (see “Results”). With regard to climate, marine and continental proxy records show a global relatively shortlived climatic warming within the last ca. 500 kyr of the Maastrichtian, followed by cooling during the ﬁnal ca. 100 kyr of the Maastrichtian persisting into the early Paleocene (Stott et al. 1990; Huber and Watkins 1992; Wilf et al. 2003b; Bowman et al. 2014; Vellekoop et al. 2017; Woelders et al. 2017; Huber et al. 2018; Hull et al. 2020). The increase in toothed and lobed leaf morphotypes across the K/Pg in Patagonia (39.7% to 60.5% and 12% to 27.9%, respectively), both of which are observed drivers of morphospace expansion in Paleogene ﬂoras, would correlate to a ca. 5°C drop in mean annual temperature, with standard caveats for paleoclimatic inference on this Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 20 ELENA STILES ET AL. basis (Wolfe 1971; Greenwood et al. 2004; Little et al. 2010). The uncertain age within the last million years of the Maastrichtian of the Leﬁpán Formation macroﬂoras studied here, however, introduces an important potential climatic bias on observed extinction that would compound the sampling bias mentioned earlier. In the Hell Creek Formation, peak richness of ﬂoral diversity (HCIII zone ﬂora) correlates with the highest temperature estimates of the late Maastrichtian, followed by a decline in species richness during rapid cooling in the terminal Maastrichtian (Wilf et al. 2003b). If a comparison were to be made solely between a collection of Maastrichtian HCIII ﬂoras from the peak of diversity of warmth and those of the Fort Union, an overestimation of extinction percentages would result. For example, if we only compare the −15 m (HCIII) and +38 m (in C29N like the PL1 ﬂora) horizons in North Dakota (Wilf et al. 2003b; Wilf and Johnson 2004), the observed dicot-leaf extinction is 99%. Although it is not possible to state the age of the Maastrichtian Leﬁpán Formation ﬂoras at this precision, their high species richness, dinoﬂagellate markers indicative of the last 0.5 Myr of the Cretaceous, and associated warm proxy temperatures (Barreda et al. 2012; Scasso et al. 2012; Vellekoop et al. 2017) suggest that they could correlate to the terminal Cretaceous warming event and thus HCIII, possibly translating into an overestimation of macroﬂoral extinction in this study on the assumption that temperature correlates with plant diversity. Conclusions We report the ﬁrst K/Pg macroﬂoral investigation in the Southern Hemisphere that is based on large, stratigraphically constrained collections. Our 92% observed macroﬂoral extinction is best viewed as a maximum because of likely geographic, stratigraphic, and paleoclimatic biases. Nonetheless, our estimate clearly reﬂects underlying high species-level turnover in Patagonia. High macroﬂoral turnover and associated insect herbivore extinction, compositionally homogeneous Danian ﬂoras, and a sharp drop in rareﬁed ﬂoral species richness in Patagonia reveal extinction and recovery patterns broadly resembling those observed in NAM and support a geographically widespread extinction event. However, Patagonian and North American turnover show contrasts. Compared with NAM ﬂoras of the WB in North Dakota, Patagonian ﬂoras are much more diverse in both Maastrichtian (Fig. 5) and Danian (Iglesias et al. 2007) assemblages. Richer Maastrichtian ﬂoras in Patagonia may have contributed to the less severe drop in overall species richness and signiﬁcantly faster Danian recovery than observed in the WB or other northern Great Plains ﬂoras. Insect herbivory observations on the same collections (Donovan et al. 2016, 2018) follow patterns similar to North American records, indicating that the macroﬂoral species extinction in Patagonia had catastrophic effects on herbivorous insect communities. However, like their host macroﬂoras, specialized insect damage types in Patagonia recover much faster than those in NAM, despite high turnover in both regions. This study reports speciose Maastrichtian macroﬂoras in Patagonia for the ﬁrst time, extending the history of elevated ﬂoral diversity in South America into the terminal Cretaceous. The limited palynological extinction and continuity of most higher taxa (families and genera) across time and space indicate persistence of major plant clades even as signiﬁcant extinction took place at the species level. Leaves with lauraceous afﬁnity are characteristically dominant in the Patagonian macroﬂoral assemblages, as in the NAM Ratón Basin, drawing an interesting parallel between the two regions. In addition to Lauraceae, we provide macroﬂoral evidence to support the survival of the families Cunoniaceae, Malvaceae, and Rosaceae in Patagonia. Morphospace analysis of Maastrichtian– Danian Patagonian macroﬂoras shows minimal character loss from the K/Pg extinction and that Danian macroﬂoras are morphologically more diverse than Maastrichtian assemblages. Danian ﬂoras rich in lobed and toothed species appear to be a notable Patagonian characteristic that contrasts with North American macroﬂoras of the WB, where lobed forms largely disappear across the K/Pg. Increased diversity of toothed species in Danian Patagonian Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION assemblages is probably related to a general climatic cooling, potentially aligning with global temperature records. Extinction and recovery in Patagonian macroﬂoras parallel North American WB assemblages in the K/Pg drop of rareﬁed species richness, low-diversity homogeneous Paleocene ﬂoras, and dramatic loss of specialized insect herbivores, indicating that terrestrial ecosystems in both areas were severely disrupted. Contrasts between Patagonian and North American macroﬂoras emerge in a faster Patagonian recovery, comparably much higher ﬂoral diversity throughout the Cretaceous–Paleogene time interval, and differences in morphological turnover. Acknowledgments We thank the technical staff of the Museo Paleontológico Egidio Feruglio (MEF), including P. Puerta, M. Caffa, E. Ruigomez, L. Reiner, and L. Canessa, as well as K. Johnson, R. Scasso, M. Donovan, and many others for their ﬁeld and laboratory assistance over several expeditions and collections visits. We thank V. Barreda for her assistance reviewing palynological records and M. Patzkowsky and T. Bralower for valuable advice during the development of this project. We thank the editors, K. Boyce and C. Looy, and V. Vajda and three anonymous reviewers for providing constructive feedback that helped us improve this article. Funding was provided to E.S. by Geological Society of America Student Research grant no.12008-18, a Mid-American Paleontological Society (MAPS) Outstanding Research Award, the Penn State Geosciences Charles E. Knopf, Sr., Memorial Scholarship, and two Penn State Geosciences Paul D. Krynine Scholarships, as well as contributions from National Science Foundation grants DEB-15556666/1556136, EAR-1925755/1925552, DEB-0919071/0918932, and DEB-0345750 that beneﬁted all authors. This work partially fulﬁlled the M.Sc. in Geosciences degree requirements of E.S. at Penn State University. Literature Cited Aberhan, M., and W. Kiessling. 2014. Rebuilding biodiversity of Patagonian marine molluscs after the end-Cretaceous mass extinction. PLoS ONE 9:e102629. 21 Alvarez, L. W., W. Alvarez, F. Asaro, and H. V. Michel. 1980. Extraterrestrial cause for the Cretaceous–Tertiary extinction. Science 208:1095–1108. Alvarez, W., F. Asaro, and A. Montanari. 1990. Iridium proﬁle for 10 million years across the Cretaceous–Tertiary boundary at Gubbio (Italy). Science 250:1700–1702. Andruchow-Colombo, A., I. H. Escapa, N. R. Cúneo, and M. A. Gandolfo. 2018. Araucaria leﬁpanensis (Araucariaceae), a new species with dimorphic leaves from the Late Cretaceous of Patagonia, Argentina. American Journal of Botany 105:1067–1087. Andruchow-Colombo, A., I. H. Escapa, R. J. Carpenter, R. S. Hill, A. Iglesias, A. M. Abarzua, and P. Wilf. 2019. Oldest record of the scale-leaved clade of Podocarpaceae, early Paleocene of Patagonia, Argentina. Alcheringa 43:127–145. Aragón, E., and M. M. Mazzoni. 1997. Geología y estratigrafía del complejo volcánico piroclástico del Rio Chubut. Revista de la Asociación Geológica Argentina 52:243–256. Aragón, E., A. Castro, J. Diaz-Alvarado, L. Pinotti, F. D’Eramo, M. Demartis, J. Coniglio, I. Hernando, and C. Rodriguez. 2018. Mantle derived crystal-poor rhyolitic ignimbrites: eruptive mechanism from geochemical and geochronological data of the Piedra Parada caldera, Southern Argentina. Geoscience Frontiers 9:1529–1553. Archangelsky, S. 1973. Palinología del Paleoceno de Chubut. I. Descripciones sistemáticas. Ameghiniana 10:339–399. Artemieva, N., and J. Morgan. 2017. Quantifying the release of climate-active gases by large meteorite impacts with a case study of Chicxulub. Geophysical Research Letters 44:10–180. Ash, A., B. Ellis, L. J. Hickey, K. R. Johnson, P. Wilf, and S. L. Wing. 1999. Manual of leaf architecture—morphological description and categorization of dicotyledonous and net-veined monocotyledonous angiosperms. Smithsonian Institution, Washington D.C. Baldoni, A. M. 1992. Palynology of the lower Leﬁpán Formation (Upper Cretaceous) of Barranca de los Perros, Chubut Province, Argentina. Part I. Cryptogam spores and gymnosperm pollen. Palynology 16:117–136. Baldoni, A. M., R. A. Askin, and A. M. Baldoni. 1993. Palynology of the lower Leﬁpán Formation (Upper Cretaceous) of Barranca de los Perros, Chubut Province, Argentina Part II. Angiosperm pollen and discussion. Palynology 17:241–264. Barclay, R. S., K. R. Johnson, W. J. Betterton, and D. L. Dilcher. 2003. Stratigraphy and megaﬂora of a K-T boundary section in the eastern Denver Basin, Colorado. Rocky Mountain Geology 38:45–71. Bardeen, C. G., R. R. Garcia, O. B. Toon, and A. J. Conley. 2017. On transient climate change at the Cretaceous–Paleogene boundary due to atmospheric soot injections. Proceedings of the National Academy of Sciences USA 114:7415–7424. Barreda, V. D., N. R. Cúneo, P. Wilf, E. D. Currano, R. A. Scasso, and H. Brinkhuis. 2012. Cretaceous/Paleogene ﬂoral turnover in Patagonia: drop in diversity, low extinction, and a Classopollis spike. PLoS ONE 7:e52455. Behrensmeyer, A. K., S. M. Kidwell, and R. A. Gastaldo. 2000. Taphonomy and paleobiology. Paleobiology 26:103–147. Bercovici, A., D. Pearson, D. Nichols, and J. Wood. 2009. Biostratigraphy of selected K/T boundary sections in southwestern North Dakota, USA: toward a reﬁnement of palynological identiﬁcation criteria. Cretaceous Research 30:632–658. Berry, E. W. 1937. Succession of fossil ﬂoras in Patagonia. Proceedings of the National Academy of Sciences USA 23:537–542. Berry, K. 2019. Linking fern foliage with spores at the K-Pg boundary section in the Sugarite coal zone, New Mexico, USA, while questioning the orthodoxy of the global pattern of plant succession across the K-Pg boundary. Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen 291:159–169. Bonaparte, J. F., L. M. Van Valen, and A. Kramartz. 1993. La fauna local de Punta Peligro, Paleoceno Inferior, de la provincia del Chubut, Patagonia, Argentina. Evolutionary Monographs 14:1–61. Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 22 ELENA STILES ET AL. Bowman, V. C., J. E. Francis, R. A. Askin, J. B. Riding, and G. T. Swindles. 2014. Latest Cretaceous–earliest Paleogene vegetation and climate change at the high southern latitudes: palynological evidence from Seymour Island, Antarctic Peninsula. Palaeogeography, Palaeoclimatology, Palaeoecology 408:26–47. Brea, M., S. D. Matheos, A. Zamuner, and D. Ganuza. 2005. Análisis de los anillos de crecimiento del bosque fósil de Victor Szlápelis, Terciario Inferior del Chubut, Argentina. Ameghiniana 42:407–418. Brooks, R. R., C. P. Strong, J. Lee, C. J. Orth, J. S. Gilmore, D. E. Ryan, and J. Holzbecher. 1986. Stratigraphic occurrences of iridium anomalies at four Cretaceous/Tertiary boundary sites in New Zealand. Geology 14:727–729. Brugger, J., G. Feulner, and S. Petri. 2017. Baby, it’s cold outside: climate model simulations of the effects of the asteroid impact at the end of the Cretaceous. Geophysical Research Letters 44:419–427. Burnham, R. J. 1993. Reconstructing richness in the plant fossil record. Palaios 8:376–384. Butler, K. L., B. K. Horton, A. Echaurren, A. Folguera, and F. Fuentes. 2019. Cretaceous–Cenozoic growth of the Patagonian broken foreland basin, Argentina: chronostratigraphic framework and provenance variations during transitions in Andean subduction dynamics. Journal of South American Earth Sciences 97:102242. Cantrill, D. J., and Poole, I. 2012. The origin of southern temperate ecosystems. Pp. 249–307 in D. J. Cantrill and I. Poole, eds. The vegetation of Antarctica through geological time. Cambridge University Press, Cambridge. Carpenter, R. J., A. Iglesias, and P. Wilf. 2018. Early Cenozoic vegetation in Patagonia: new insights from organically preserved plant fossils (Ligorio Márquez Formation, Argentina). International Journal of Plant Sciences 179:115–135. Casal, G. A., Allard, J. O., and Foix, N., 2015, Análisis estratigráﬁco y paleontológico del Cretácico superior en la cuenca del golfo San Jorge: nueva unidad litoestratigráﬁca para el Grupo Chubut. Revista de la Asociación Geológica Argentina 72:77–95. Case, J. A., and M. O. Woodburne. 1986. South American marsupials: a successful crossing of the Cretaceous–Tertiary boundary. Palaios 1:413–416. Clyde, W. C., P. Wilf, A. Iglesias, R. L. Slingerland, T. Barnum, P. K. Bijl, T. J. Bralower, H. Brinkhuis, E. E. Comer, B. T. Huber, M. Ibañez-Mejia, B. R. Jicha, J. M. Krause, J. D. Schueth, B. S. Singer, M. S. Raigemborn, M. D. Schmitz, A. Sluijs, and M. C. Zamaloa. 2014. New age constraints for the Salamanca Formation and lower Río Chico Group in the western San Jorge Basin, Patagonia, Argentina: implications for Cretaceous–Paleogene extinction recovery and land mammal age correlations. Geological Society of America Bulletin 126:289–306. Comer, E. E., R. L. Slingerland, J. M. Krause, A. Iglesias, W. C. Clyde, M. S. Raigemborn, and P. Wilf. 2015. Sedimentary facies and depositional environments of diverse early Paleocene ﬂoras, north-central San Jorge Basin, Patagonia, Argentina. Palaios 30:553–573. Donovan, M. P., P. Wilf, C. C. Labandeira, K. R. Johnson, and D. J. Peppe. 2014. Novel insect leaf-mining after the end-Cretaceous extinction and the demise of Cretaceous leaf miners, Great Plains, USA. PLoS ONE 9:e103542. Donovan, M. P., A. Iglesias, P. Wilf, C. C. Labandeira, and N. R. Cúneo. 2016. Rapid recovery of Patagonian plant-insect associations after the end-Cretaceous extinction. Nature Ecology & Evolution 1:0012. Donovan, M. P., A. Iglesias, P. Wilf, C. C. Labandeira, and N. R. Cúneo. 2018. Diverse plant-insect associations from the latest Cretaceous and early Paleocene of Patagonia, Argentina. Ameghiniana 55:303–338. Ellis, B., D. C. Daly, L. J. Hickey, K. R. Johnson, J. D. Mitchell, P. Wilf, and S. L. Wing. 2009. Manual of leaf architecture. Cornell University Press, Ithaca, N.Y. Erwin, D. H. 2002. Lessons from the past: biotic recoveries from mass extinctions. Proceedings of the National Academy of Sciences USA 98:5399–5403. Escapa, I. H., A. Iglesias, P. Wilf, S. A. Catalano, M. A. Caraballo-Ortiz, and N. Rubén Cúneo. 2018. Agathis trees of Patagonia’s Cretaceous–Paleogene death landscapes and their evolutionary signiﬁcance. American Journal of Botany 105:1345–1368. Figari, E. G., R. A. Scasso, N. R. Cúneo, and I. H. Escapa. 2015. Estratigrafía y evolución geológica de la Cuenca de Cañadón Asfalto, Provincia del Chubut, Argentina. Latin American Journal of Sedimentology and Basin Analysis 22:135–169. Flynn, A. G., and D. J. Peppe. 2019. Early Paleocene tropical forest from the Ojo Alamo Sandstone, San Juan Basin, New Mexico, USA. Paleobiology 45:612–635. Foote, M. 1993. Discordance and concordance between morphological and taxonomic diversity. Paleobiology 19:185–204. Foote, M. 1994. Morphological disparity in Ordovician–Devonian crinoids and the early saturation of morphological space. Paleobiology 20:320–344. Futey, M. K., M. A. Gandolfo, M. C. Zamaloa, R. Cúneo, and G. Cladera. 2012. Arecaceae fossil fruits from the Paleocene of Patagonia, Argentina. Botanical Review 78:205–234. Gelfo, J. N., F. J. Goin, M. O. Woodburne, and C. D. E. Muizon. 2009. Biochronological relationships of the earliest South American Paleogene mammalian faunas. Palaeontology 52:251–269. Gerber, S. 2019. Use and misuse of discrete character data for morphospace and disparity analyses. Palaeontology 62:305–319. Givnish, T. J., and R. Kriebel. 2017. Causes of ecological gradients in leaf margin entirety: evaluating the roles of biomechanics, hydraulics, vein geometry, and bud packing. American Journal of Botany 104:354–366. Goin, F. J., R. Pascual, M. F. Tejedor, J. N. Gelfo, M. O. Woodburne, J. A. Case, M. A. Reguero, M. Bond, G. M. López, A. L. Cione, D. U. Sauthier, L. Balarino, R. A. Scasso, F. A. Medina, and M. C. Ubaldón. 2006. The earliest Tertiary therian mammal from South America. Journal of Vertebrate Paleontology 26:505–510. Goin, F. J., M. F. Tejedor, L. Chornogubsky, M. López, J. N. Gelfo, and M. O. Woodburne. 2012. Persistence of a Mesozoic, nontherian mammalian lineage (Gondwanatheria) in the midPaleogene of Patagonia. Naturwissenschaften 99:449–463. Gradstein, F. M., Ogg, J. G., Schmitz, M. D., and Ogg, G., eds. 2012, The geologic time scale 2012. Elsevier, Amsterdam, Netherlands. Greenwood, D. R., S. L. Wing, and D. C. Christophel. 2004. Paleotemperature estimation using leaf margin analysis: is Australia different? Palaios 19:129–142. Hickey, L. J., and J. A. Wolfe. 1975. The bases of angiosperm phylogeny: vegetative morphology. Annals of the Missouri Botanical Garden 62:538–589. Hicks, J. F., K. R. Johnson, J. D. Obradovich, L. Tauxe, and D. P. Clark. 2002. Magnetostratigraphy and geochronology of the Hell Creek and basal Fort Union formations of southwestern North Dakota and a recalibration of the age of the Cretaceous– Tertiary boundary. Geological Society of America Special Paper 361:35–55. Hotton, C. L. 2002. Palynology of the Cretaceous–Tertiary boundary in central Montana: evidence for extraterrestrial impact as a cause of the terminal Cretaceous extinctions. Geological Society of America Special Paper 361:473–501. Hsieh, T. C., K. H. Ma, and A. Chao. 2016. iNEXT: an R package for rarefaction and extrapolation of species diversity (Hill numbers). Methods in Ecology and Evolution 7:1451–1456. Huber, B. T., and D. K. Watkins. 1992. Biogeography of Campanian–Maastrichtian calcareous plankton in the region of the Southern Ocean: paleogeographic and paleoclimatic implications. Antarctic Research Series 56:31–60. Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION Huber, B. T., K. G. MacLeod, D. K. Watkins, and M. F. Cofﬁn. 2018. The rise and fall of the Cretaceous hot greenhouse climate. Global and Planetary Change 167:1–23. Hull, P. M., A. Bornemann, D. E. Penman, M. J. Henehan, R. D. Norris, P. A. Wilson, P. Blum, L. Alegret, S. J. Batenburg, P. R. Bown, T. J. Bralower, C. Cournede, A. Deutsch, B. Donner, O. Friedrich, S. Jehle, H. Kim, D. Kroon, P. Lippert, D. Loroch, I. Moebius, K. Moriya, D. Peppe, G. E. Ravizza, U. Röhl, J. Schueth, J. Sepúlveda, P. Sexton, E. Sibert, K. Sliwinska, R. E. Summons, E. Thomas, T. Westerhold, J. H. Whiteside, T. Yamaguchi, and J. C. Zachos. 2020. On impact and volcanism across the Cretaceous–Paleogene boundary. Science 367:266–272. Iglesias, A. 2007. Estudio paleobotánico, paleoecológico y paleoambiental en secuencias de la Formación Salamanca, del Paleoceno Inferior en el sur de la Provincia de Chubut, Patagonia, Argentina. Ph.D. thesis, Universidad Nacional de La Plata, La Plata, Argentina. Iglesias, A., P. Wilf, K. R. Johnson, N. R. Cúneo, and S. D. Matheos. 2007. A Paleocene lowland macroﬂora from Patagonia reveals signiﬁcantly greater richness than North American analogs. Geology 35:947–950. Jablonski, D. 2005. Mass extinctions and macroevolution. Paleobiology 31:192–210. Jiang, S., T. J. Bralower, M. E. Patzkowsky, L. R. Kump, and J. D. Schueth. 2010. Geographic controls on nannoplankton extinction across the Cretaceous/Palaeogene boundary. Nature Geoscience 3:280–285. Johnson, K. R. 1992. Leaf-fossil evidence for extensive ﬂoral extinction at the Cretaceous–Tertiary boundary, North Dakota, USA. Cretaceous Research 13:91–117. Johnson, K. R. 2002. Megaﬂora of the Hell Creek and lower Fort Union formations in the Western Dakotas: vegetational response to climate change, the Cretaceous–Tertiary boundary event, and rapid marine transgression. Geological Society of America Special Paper 361:329–391. Johnson, K. R., and B. Ellis. 2002. A tropical rainforest in Colorado 1.4 million years after the Cretaceous–Tertiary boundary. Science 296:2379–2383. Johnson, K. R., and L. J. Hickey. 1990. Megaﬂoral change across the Cretaceous/Tertiary boundary in the northern Great Plains and Rocky Mountains, U.S.A. Geological Society of America Special Paper 247:433–444. Johnson, K. R., D. J. Nichols, M. Attrep, and C. J. Orth. 1989. Highresolution leaf-fossil record spanning the Cretaceous/Tertiary boundary. Nature 340:708–711. Jud, N. A., M. A. Gandolfo, A. Iglesias, and P. Wilf. 2017. Flowering after disaster early Danian buckthorn (Rhamnaceae) ﬂowers and leaves from Patagonia. PLoS ONE 12:e0176164. Jud, N. A., M. A. Gandolfo, A. Iglesias, and P. Wilf. 2018a. Fossil ﬂowers from the early Palaeocene of Patagonia, Argentina, with afﬁnity to Schizomerieae (Cunoniaceae). Annals of Botany 121:431–442. Jud, N. A., A. Iglesias, P. Wilf, and M. A. Gandolfo. 2018b. Fossil moonseeds from the Paleogene of west Gondwana (Patagonia, Argentina). American Journal of Botany 105:927–942. Kennedy, E. M., R. A. Spicer, and P. M. Rees. 2002. Quantitative palaeoclimate estimates from Late Cretaceous and Paleocene leaf ﬂoras in the northwest of the South Island, New Zealand. Palaeogeography, Palaeoclimatology, Palaeoecology 184:321–345. Krause, J. M., W. C. Clyde, M. Ibañez-Mejia, M. D. Schmitz, T. Barnum, E. S. Bellosi, and P. Wilf. 2017. New age constraints for early Paleogene strata of central Patagonia, Argentina: implications for the timing of South American Land Mammal Ages. Geological Society of America Bulletin 129:886–903. Krug, A. Z., D. Jablonski, and J. W. Valentine. 2017. Signature of the end-Cretaceous mass extinction in the modern biota. Science 323:767–771. 23 Labandeira, C. C., K. R. Johnson, and P. Wilf. 2002. Impact of the terminal Cretaceous event on plant–insect associations. Proceedings of the National Academy of Sciences USA 99:2061–2066. Legarreta, L., and M. A. Uliana. 1994. Asociaciones de fósiles y hiatos en el Supracretácico-Neógeno de Patagonia: una perspectiva estratigrafo-secuencial. Ameghiniana 31:257–281. Lerbekmo, J. F., and R. M. St. Louis. 1986. The terminal Cretaceous iridium anomaly in the Red Deer Valley, Alberta, Canada. Canadian Journal of Earth Sciences 23:120–124. Little, S. A., S. W. Kembel, and P. Wilf. 2010. Paleotemperature proxies from leaf fossils reinterpreted in light of evolutionary history. PLoS ONE 5:e15161. Lyson, T. R., I. M. Miller, A. D. Bercovici, K. Weissenburger, A. J. Fuentes, W. C. Clyde, J. W. Hagadorn, M. J. Butrim, K. R. Johnson, R. F. Fleming, R. S. Barclay, S. A. Maccracken, B. Lloyd, G. P. Wilson, D. W. Krause, and S. G. B. Chester. 2019. Exceptional continental record of biotic recovery after the Cretaceous–Paleogene mass extinction. Science 983:977–983. Martínez, C., M. A. Gandolfo, and N. R. Cúneo. 2018. Angiosperm leaves and cuticles from the uppermost Cretaceous of Patagonia, biogeographic implications and atmospheric paleo-CO2 estimates. Cretaceous Research 89:107–118. McCune, B. 1994. Improving community analysis with the Beals smoothing function. Ecoscience 1:82–86. McLoughlin, S., R. J. Carpenter, G. J. Jordan, and R. S. Hill. 2008. Seed ferns survived the end-Cretaceous mass extinction in Tasmania. American Journal of Botany 95:465–471. McLoughlin, S., R. J. Carpenter, and C. Pott. 2011. Ptilophyllum muelleri (Ettingsh.) comb. nov. from the Oligocene of Australia. Last of the Bennettitales? International Journal of Plant Sciences 172:574–585. Medina, F. A., and H. H. Camacho. 1990. Bioestratigrafía del Cretácico superior-Paleoceno marino de la Formación Leﬁpán, Barranca de los Perros, Río Chubut, Chubut. V0 Congreso Argentino de Paleontología y Bioestratigrafía, Actas 7:137–142. San Miguel de Tucumán, Argentina. Mitteroecker, P., and S. M. Huttegger. 2009. The concept of morphospaces in evolutionary and developmental biology: mathematics and metaphors. Biological Theory 4:54–67. Münzbergová, Z., and T. Herben. 2004. Identiﬁcation of suitable unoccupied habitats in metapopulation studies using co-occurrence of species. Oikos 105:408–414. Nichols, D. J. 2002. Palynology and palynostratigraphy of the Hell Creek Formation in North Dakota: a microfossil record of plants at the end of Cretaceous time. Geological Society of America Special Paper 361:393–456. Nichols, D. J., and R. F. Fleming. 1990. Plant microfossil record of the terminal Cretaceous event in the western United States and Canada. Geological Society of America Special Paper 247:445–469. Nichols, D. J., and K. R. Johnson. 2008. Plants and the K-T boundary. Cambridge University Press, Cambridge. Nichols, D. J., D. M. Jarzen, C. J. Orth, and P. Q. Oliver. 1986. Palynological and iridium anomalies at Cretaceous-Tertiary boundary, south-central Saskatchewan. Science 231:714–717. Oksanen, J., F. G. Blanchet, M. Friendly, R. Kindt, P. Legendre, D. McGlinn, P. R. Minchin, R. B. O’Hara, G. L. Simpson, P. H. Solymos, M. H. Stevens, E. Szoecs, and H. Wagner. 2017. vegan: community ecology package. http://cran.r-project.org. Orth, C. J., J. S. Gilmore, J. D. Knight, C. L. Pillmore, R. H. Tschudy, and J. E. Fassett. 1981. An iridium abundance anomaly at the palynological Cretaceous–Tertiary boundary in northern New Mexico. Science 214:1341–1343. Palazzesi, L., and V. Barreda. 2007. Major vegetation trends in the Tertiary of Patagonia (Argentina): a qualitative paleoclimatic approach based on palynological evidence. Flora 202:328–337. Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 24 ELENA STILES ET AL. Paradis, E., and K. Schliep. 2018. ape 5.0: an environment for modern phylogenetics and evolutionary analyses in R. Bioinformatics 35:526–528. Pascual, R., M. Archer, E. Ortiz Jaureguizar, J. L. Prado, H. Godthelp, and S. Hand. 1992. First discovery of monotremes in South America. Nature 356:704–706. Petriella, B., and S. Archangelsky. 1975. Vegetación y ambientes en el Paleoceno de Chubut. Actas del Primer Congreso Argentino de Paleontología y Bioestratigrafía 1:257–270. San Miguel de Tucumán, Argentina. Pole, M., and V. Vajda. 2009. A new terrestrial Cretaceous–Paleogene site in New Zealand—turnover in macroﬂora conﬁrmed by palynology. Cretaceous Research 30:917–938. Prinn, R. G., and B. Fegley Jr. 1987. Bolide impacts, acid rain, and biospheric traumas at the Cretaceous–Tertiary boundary. Earth and Planetary Science Letters 83:1–15. Quiroga, M. P., P. Mathiasen, A. Iglesias, R. R. Mill, and A. C. Premoli. 2015. Molecular and fossil evidence disentangle the biogeographical history of Podocarpus, a key genus in plant geography. Journal of Biogeography 43:372–383. Raigemborn, M., M. Brea, A. Zucol, and S. Matheos. 2009. Early Paleogene climate at mid latitude in South America: mineralogical and paleobotanical proxies from continental sequences in Golfo San Jorge basin (Patagonia, Argentina). Geologica Acta 7:125–145. Raigemborn, M. S., J. M. Krause, E. S. Bellosi, and S. D. Matheos. 2010. Redeﬁnición estratigráﬁca del grupo Río Chico (Paleógeno Inferior), en el norte de la cuenca del Golfo de San Jorge, Chubut. Revista de la Asociación Geológica Argentina 67:239–256. Raup, D. M., and J. J. Sepkoski. 1982. Mass extinctions in the fossil record. Science 215:1501–1503. Robertson, D. S., W. M. Lewis, P. M. Sheehan, and O. B. Toon. 2013. K-Pg extinction patterns in marine and freshwater environments: the impact winter model. Journal of Geophysical Research: Biogeosciences 118:1006–1014. Roy, K., and M. Foote. 1997. Morphological approaches to measuring biodiversity. Trends in Ecology and Evolution 12:277–281. Ruiz, D. P., M. Brea, M. S. Raigemborn, and S. D. Matheos. 2017. Conifer woods from the Salamanca Formation (early Paleocene), central Patagonia, Argentina: paleoenvironmental implications. Journal of South American Earth Sciences 76:427–445. Ruiz, D. P., M. S. Raigemborn, M. Brea, and R. R. Pujana. 2020. Paleocene Las Violetas fossil forest: wood anatomy and paleoclimatology. Journal of South American Earth Sciences 98:102414. Sauquet, H., and S. Magallón. 2018. Key questions and challenges in angiosperm macroevolution. New Phytologist 219:1170–1187. Scasso, R. A., M. Aberhan, L. Ruiz, S. Weidemeyer, F. A. Medina, and W. Kiessling. 2012. Integrated bio- and lithofacies analysis of coarse-grained, tide-dominated deltaic environments across the Cretaceous/Paleogene boundary in Patagonia, Argentina. Cretaceous Research 36:37–57. Scasso, R. A., M. B. Prámparo, J. Vellekoop, C. Franzosi, L. N. Castro, and J. S. Sinninghe Damsté. 2020. A high-resolution record of environmental changes from a Cretaceous–Paleogene section of Seymour Island, Antarctica. Palaeogeography, Palaeoclimatology, Palaeoecology 555:e109844. Schueth, J. D., T. J. Bralower, S. Jiang, and M. E. Patzkowsky. 2015. The role of regional survivor incumbency in the evolutionary recovery of calcareous nannoplankton from the Cretaceous/ Paleogene (K/Pg) mass extinction. Paleobiology 41:661–679. Schulte, P., L. Alegret, I. Arenillas, J. A. Arz, P. J. Barton, P. R. Bown, T. J. Bralower, G. L. Christeson, P. Claeys, C. S. Cockell, G. S. Collins, A. Deutsch, T. J. Goldin, K. Goto, J. M. Grajales-Nishimura, R. A. F. Grieve, S. P. S. Gulick, K. R. Johnson, W. Kiessling, C. Koeberl, D. A. Kring, K. G. MacLeod, T. Matsui, J. Melosh, A. Montanari, J. V. Morgan, C. R. Neal, D. J. Nichols, R. D. Norris, E. Pierazzo, G. Ravizza, M. Rebolledo-Vieyra, W. U. Reimold, E. Robin, T. Salge, R. P. Speijer, A. R. Sweet, J. Urrutia-Fucugauchi, V. Vajda, M. T. Whalen, and P. S. Willumsen. 2010. The Chicxulub asteroid impact and mass extinction at the Cretaceous–Paleogene boundary. Science 327:1214–1218. Schultz, P. H., and S. L. D’Hondt. 1996. The Chicxulub impact angle and its consequences. Geology 24:963–967. Spalletti, L. A. 1996. Estuarine and shallow-marine sedimentation in the Upper Cretaceous–Lower Tertiary west-central Patagonian Basin (Argentina). Geological Society of America Special Publications 117:81–93. Sterli, J., and M. S. de la Fuente. 2019. Cranial and post-cranial remains and phylogenetic relationships of the Gondwanan meiolaniform turtle Peligrochelys walshae from the Paleocene of Chubut, Argentina. Journal of Paleontology 93:798–821. Stott, L. D., J. P. Kennett, N. J. Shackleton, and R. M. Corﬁeld. 1990. The evolution of Antarctic surface waters during the Paleogene: inferences from the stable isotopic composition of planktonic foraminifers, ODP leg 1131. Proceedings of the Ocean Drilling Program, Scientiﬁc Results 113:849–863. Sweet, A. R., and D. R. Braman. 2001. Cretaceous–Tertiary palynoﬂoral perturbations and extinctions within the Aquilapollenites phytogeographic province. Canadian Journal of Earth Sciences 38:249–269. Sweet, A. R., D. R. Braman, and J. F. Lerbekmo. 1990. Palynoﬂoral response to K/T boundary events: a transitory interruption within a dynamic system. Geological Society of America Special Paper 247:457–469 Sweet, A. R., D. R. Braman, and J. F. Lerbekmo. 1999. Sequential palynological changes across the composite Cretaceous–Tertiary (K-T) boundary claystone and contiguous strata, western Canada and Montana, U.S.A. Canadian Journal of Earth Sciences 36:743– 767. Sylwan, C. A. 2001. Geology of the Golfo San Jorge Basin, Argentina. Journal of Iberian Geology 27:123–157. Tabor, C. R., C. G. Bardeen, B. L. Otto-Bliesner, R. R. Garcia, and O. B. Toon. 2020. Causes and climatic consequences of the impact winter at the Cretaceous–Paleogene boundary. Geophysical Research Letters 47:e60121. Tipper, J. C. 1979. Rarefaction and rareﬁction—the use and abuse of a method. Paleobiology 5:423–434. Tyrrell, T., A. Merico, and D. I. Armstrong McKay. 2015. Severity of ocean acidiﬁcation following the end-Cretaceous asteroid impact. Proceedings of the National Academy of Sciences USA 112:6556–6561. Upchurch, G. R. J. 1995. Dispersed angiosperm cuticles: their history, preparation, and application to the rise of angiosperms in Cretaceous and Paleocene coals, southern western interior of North America. International Journal of Coal Geology 28:161–227. Vajda, V., and A. Bercovici. 2014. The global vegetation pattern across the Cretaceous–Paleogene mass extinction interval: a template for other extinction events. Global and Planetary Change 122:29–49. Vajda, V., and J. I. Raine. 2003. Pollen and spores in marine Cretaceous/Tertiary boundary sediments at mid-Waipara River, North Canterbury, New Zealand. New Zealand Journal of Geology and Geophysics 46:255–273. Vajda, V., J. I. Raine, and C. J. Hollis. 2001. Indication of global deforestation at the Cretaceous–Tertiary boundary by New Zealand fern spike. Science 294:1700–1702. Vajda-Santivanez, V. 1999. Miospores from upper Cretaceous– Paleocene strata in northwestern Bolivia. Palynology 23:181–196. Vellekoop, J., A. Sluijs, J. Smit, S. Schouten, J. W. H. Weijers, J. S. Sinninghe Damste, and H. Brinkhuis. 2014. Rapid short-term cooling following the Chicxulub impact at the Cretaceous–Paleogene boundary. Proceedings of the National Academy of Sciences USA 111:7537–7541. Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45 PATAGONIAN K/PG PLANT EXTINCTION Vellekoop, J., F. Holwerda, M. B. Prámparo, V. Willmott, S. Schouten, N. R. Cúneo, R. A. Scasso, and H. Brinkhuis. 2017. Climate and sea-level changes across a shallow marine Cretaceous-Palaeogene boundary succession in Patagonia, Argentina. Palaeontology 60:519–534. Volkheimer, W., L. Scafati, and D. L. Melendi. 2007. Palynology of a Danian warm climatic wetland in central northern Patagonia, Argentina. Revista Española de Micropaleontología 39:117–134. Wilf, P. 1997. When are leaves good thermometers? A new case for leaf margin analysis. Paleobiology 23:373–390. Wilf, P., and K. R. Johnson. 2004. Land plant extinction at the end of the Cretaceous: a quantitative analysis of the North Dakota megaﬂoral record. Paleobiology 30:347–368. Wilf, P., N. R. Cúneo, K. R. Johnson, J. F. Hicks, S. L. Wing, and J. D. Obradovich. 2003a. High plant diversity in Eocene South America: evidence from Patagonia. Science 300:122–125. Wilf, P., K. R. Johnson, and B. T. Huber. 2003b. Correlated terrestrial and marine evidence for global climate changes before mass extinction at the Cretaceous–Paleogene boundary. Proceedings of the National Academy of Sciences USA 100:599–604. Wilf, P., K. R. Johnson, N. R. Cúneo, M. E. Smith, B. S. Singer, and M. A. Gandolfo. 2005. Eocene plant diversity at Laguna del Hunco and Río Pichileufú, Patagonia, Argentina. American Naturalist 165:634–650. Wilf, P., M. P. Donovan, N. R. Cúneo, and M. A. Gandolfo. 2017. The fossil ﬂip-leaves (Retrophyllum, Podocarpaceae) of southern South America. American Journal of Botany 104:1344–1369. 25 Wills, M. A., D. E. G. Briggs, and R. A. Fortey. 1994. Disparity as an evolutionary index: a comparison of Cambrian and recent arthropods. Paleobiology 20:93–130. Woelders, L., J. Vellekoop, D. Kroon, J. Smith, S. Casadío, M. B. Prámparo, J. Dinares-Turell, F. Peterse, A. Sluijs, J. T. Lenaerts, and R. P. Speijer. 2017. Latest Cretaceous climatic and environmental change in the South Atlantic region. Paleoceanography 32:466–483. Wolfe, J. A. 1971. Tertiary climatic ﬂuctuations and methods of analysis of Tertiary ﬂoras. Palaeogeography, Palaeoclimatology, Palaeoecology 9:27–57. Wolfe, J. A. 1987. Late Cretaceous–Cenozoic history of deciduousness and the terminal Cretaceous event. Paleobiology 13:215–226. Wolfe, J. A. 1995. Paleoclimatic estimates from Tertiary leaf assemblages. Annual Review of Earth and Planetary Sciences 23:119– 142. Wolfe, J. A., and G. R. Upchurch. 1986. Vegetation, climatic and ﬂoral changes at the Cretaceous–Tertiary boundary. Nature 324:148–152. Zamaloa, M. del C., and R. Andreis. 1995. Asociación palinológica del Paleoceno Temprano (Formación Salamanca) en Ea. Laguna Manantiales, Santa Cruz, Argentina. VI Congreso Argentino de Paleontología y Bioestratigrafía 1:301–305. Trelew, Argentina. Zamuner, A., M. Brea, D. Ganuza, and S. Matheos. 2000. Resultados anatómico-sistemáticos preliminares en la lignoﬂora del Bosque de Szlápelis (Terciario Inferior), Provincia del Chubut, Argentina. Ameghiniana, Suplemento Resúmenes 37:80R. Downloaded from https://www.cambridge.org/core. Universiteitsbibliotheek Utrecht, on 08 Oct 2020 at 11:47:22, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/pab.2020.45

American Journal of Botany 101(1): 156–179. 2014. FIRST SOUTH AMERICAN AGATHIS (ARAUCARIACEAE), EOCENE OF PATAGONIA1 PETER WILF2,7, IGNACIO H. ESCAPA3, N. RUBÉN CÚNEO3, ROBERT M. KOOYMAN4, KIRK R. JOHNSON5, AND ARI IGLESIAS6 2Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802 USA; 3Museo Paleontológico Egidio Feruglio, Consejo Nacional de Investigaciones Científicas y Técnicas, Trelew 9100, Chubut, Argentina; 4National Herbarium of New South Wales, Royal Botanic Gardens and Domain Trust, Mrs Macquaries Road, Sydney 2000, New South Wales, Australia; 5National Museum of Natural History, Smithsonian Institution, Box 37012 MRC 106, Washington, D.C. 20013 USA; and 6División Paleontología, Universidad Nacional del Comahue, Instituto de Investigaciones en Biodiversidad y Ambiente–Consejo Nacional de Investigaciones Científicas y Técnicas, San Carlos de Bariloche 8400, Río Negro, Argentina. • Premise of the study: Agathis is an iconic genus of large, ecologically important, and economically valuable conifers that range over lowland to upper montane rainforests from New Zealand to Sumatra. Exploitation of its timber and copal has greatly reduced the genus’s numbers. The early fossil record of Agathis comes entirely from Australia, often presumed to be its area of origin. Agathis has no previous record from South America. • Methods: We describe abundant macrofossils of Agathis vegetative and reproductive organs, from early and middle Eocene rainforest paleofloras of Patagonia, Argentina. The leaves were formerly assigned to the New World cycad genus Zamia. • Key results: Agathis zamunerae sp. nov. is the first South American occurrence and the most complete representation of Agathis in the fossil record. Its morphological features are fully consistent with the living genus. The most similar living species is A. lenticula, endemic to lower montane rainforests of northern Borneo. • Conclusions: Agathis zamunerae sp. nov. demonstrates the presence of modern-aspect Agathis by 52.2 mya and vastly increases the early range and possible areas of origin of the genus. The revision from Zamia breaks another link between the Eocene and living floras of South America. Agathis was a dominant, keystone element of the Patagonian Eocene floras, alongside numerous other plant taxa that still associate with it in Australasia and Southeast Asia. Agathis extinction in South America was an integral part of the transformation of Patagonian biomes over millions of years, but the living species are disappearing from their ranges at a far greater rate. Key words: Río Pichileufú. Agathis; Araucariaceae; Argentina; Borneo; conifers; Eocene; extinction; Laguna del Hunco; rainforests; Agathis R. A. Salisbury (Araucariaceae; kauri, dammar) is one of the most impressive and valuable tree genera in the world, but little is known about its evolutionary and biogeographic history. Several recent molecular-clock studies have given a wide range of estimates of its age (Knapp et al., 2007; Biffin et al., 2010; Crisp and Cook, 2011; Leslie et al., 2012). We begin with a brief introduction to living Agathis, followed by an overview of its limited fossil record, which was, until now, entirely from Australia and New Zealand. Living Agathis—Agathis has ca. 17 species distributed across lowland to upper montane rainforests in Australasia and Southeast Asia (Table 1). Agathis has broad leaves, outlives most competing canopy angiosperms, and characteristically emerges above them at giant size (several species reach 50–65 m height). The genus is a backbone element of forest architecture and element cycling, supports diverse epiphytes and fungi, and is an important source of animal food, shade, roosting space, and shelter (Dumbleton, 1952; Mirams, 1957; Wise, 1962; Ripley, 1964; Gorman, 1975; Towns, 1981; Ecroyd, 1982; Enright and Ogden, 1987; Bishop, 1992; Greene, 1998; Silvester and Orchard, 1999; Jongkind et al., 2007; Verkaik and Braakhekke, 2007; Wyse, 2012). Most areas where Agathis grows are rainforests with many rare or endemic species of plants and animals (e.g., Enright, 1995; Wong and Phillipps, 1996; Morrogh-Bernard et al., 2003; Balete et al., 2009; Wilcove et al., 2013). Agathis can be an important component of tropical peatlands (Yii, 1995), whose organic carbon flux has increased ca. 32% since 1990 in Southeast Asia as a result of disturbance (Moore et al., 2013). Thus, Agathis removal and related disturbance on a large scale are likely to have significant detrimental effects on carbon balance, biodiversity, and ecosystem structure and function. Human impacts on Agathis populations are indeed enormous (Whitmore, 1977, 1980a; Bowen and Whitmore, 1980a, 1980b; 1 Manuscript received 9 September 2013; revision accepted 21 November 2013. The authors thank M. Caffa, L. Canessa, B. Cariglino, M. Carvalho, M. Gandolfo, C. González, R. Horwitt, M. Gandolfo, E. Hermsen, K. Kitayama, S. Little, H. Mujih, P. Puerta, L. Reiner, E. Ruigómez, and S. Wing for their extraordinary assistance in the field and laboratory and/or helpful and timely comments; the staff at CANB (B. Lepschi and C. Cargill), NSW (L. L. Lee and L. Murray), US (A. Clark, I. Lin, K. Rankin, and R. Russell), and USNM (J. Wingerath) for expediting specimen access and loans; and the Nahueltripay family and Instituto de Investigaciones Aplicadas for land access. This work received primary support from National Science Foundation grants DEB-0919071, DEB-0918932, and DEB-0345750 and from the David and Lucile Packard Foundation, as well as early support from National Geographic Society grant 7337-02, the University of Pennsylvania Research Foundation, and the Andrew W. Mellon Foundation. 7 Author for correspondence (e-mail: pwilf@psu.edu) doi:10.3732/ajb.1300327 American Journal of Botany 101(1): 156–179, 2014; http://www.amjbot.org/ © 2014 Botanical Society of America 156 January 2014] TABLE 1. Agathis zamunerae sp. nov., general features compared with the 17 living Agathis species. Leaves Species, range bract pairs bracts, i or s Cone scale Seed body Larger seed wing length ms arr ms height ms width shape length length width length width length width e, l 24–132 2.2–7.3 3 i 23–56 i 1.5–2.1 1.3–2.0 19–26 21–36 11.8 ca. 7 13.4 8.1 e, l 30–80 2–3 4–5 i 9–16 i 0.5–0.7 0.6–0.8 16–23 23–30 7–9 4–5 12–15 8 l, o 23–70 5–15 3 i 30–50 i 2.1–2.7 1.8–2.5 ~20 ~30 8–10 5 12 8 e, l, o 25–140 1–8 2 s 20–90 i 5–6 4–8 ~35 35–45 12–15 7–8 20 13 l, o, o–e 25–140 0–5 2–4 s 10–40 i 1–1.5 2–2.5 ~35 35–45 12–15 7–8 20 13 l–o, o o, ob, o–l 20–80 20–90 2–15 2–5 2 2–3 s s 10–40 10–30 i i 1.5 1.2–1.6 2 1.6–1.8 ~30 ~30 ~40 40–45 11–13 11–13 7–8 7–8 15 15–20 10 10–12 e, l, l–o 50–140 2–10 4 i, s 22–30 t 0.7–1.0 1–1.5 ~30 35–40 12 7 20 15 l 60–130 4–5 4 s 20–25 t 0.5–1.8 <1.6 ~25 30–35 12–15 7 20 13 e, l, len, o–e l, o–l, ob 50–110 25–170 2–10 0–7 2–3 4 i i 10–40 20–45 i i 1.5–2 1.8–2.2 2–2.5 1.4–2.2 25–30 ~35 30–35 35–45 10 12–15 6 7–8 15 20–25 8 10–15 e, l 30–90 0–1 4–5 i 10–16 t 0.5–0.7 0.5 25–35 33–45 10–12 6–8 20–25 10–13 o, o–len 55–110 ~0 5–8 i 40–70 i 2.2–2.5 2.0–2.6 ~30 ~30 6–8 5 n/a n/a e, l, o–e 45–200 1–12 4–8 i 25–50 i 0.8–2 1–3 30–40 30–40 15–20 8–10 20–30 15–20 l, o, ~orb 20–70 2–3 2–3 s 6–15 i 1 1.2–1.5 ~20 ~30 10 6 12 6 ob–tr, ob–tr, ~orb 40–85 4–20 4–5 i 30–50 i 1.8–4.5 2–4.5 16–20 22–26 9–11 7–8 15–20 9–12 e, l, obl 50–140 2–18 4–5 i, s 40–70 i/t 0.7–1.5 1–2 ~30 35–42 12–14 7–8 20–25 12–15 l, o 40–120 0–6 2–3 ~i 35–60 i/t 2.1–2.5 1.8–2.5 ~35 40–50 12–15 7–8 20–25 13–17 WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA Agathis zamunerae Wilf, sp. nov., Patagonia A. atropurpurea B. Hyland, Austr. A. australis (D. Don) Lindl., New Zealand A. borneensis Warb., Borneo to Sumatra A. dammara (Lamb.) Rich. & A. Rich., Malesia A. flavescens Ridl., Malaysia A. kinabaluensis de Laub., Borneo A. labillardierei Warb., New Guinea A. lanceolata (Sébert & Pancher) Warb., New Cal. A. lenticula de Laub., Borneo A. macrophylla (Lindl.) Mast., Fiji, Vanuatu, Solomons A. microstachya J. F. Bailey & C. T. White, Austr. A. montana de Laub., New Cal. A. moorei (Lindl.) Mast., New Cal. A. orbicula de Laub., Borneo A. ovata (C. Moore ex Vieill.) Warb., New Cal. A. robusta (C. Moore ex F. Muell.) F. M. Bailey, Austr., New Guinea A. silbae de Laub., Vanuatu Pollen cones ped length Notes: Extant species data from Farjon (2010). All measurements in millimeters. Abbreviations: arr, arrangement; Austr., Australia; br, bract; e, elliptic; i, imbricate; l, lanceolate; len, lensshaped; ms, microsporophyll; New Cal., New Caledonia; o, ovate; ob, obovate; obl, oblanceolate; orb, orbicular; ped, peduncle; s, spreading; t, tessellate; tr, truncate. 157 158 AMERICAN JOURNAL OF BOTANY [Vol. 101 Figs. 1–7. Agathis zamunerae sp. nov., leafy twigs. Figs. 1 and 2, Río Pichileufú. Figs. 3–7, Laguna del Hunco. 1, 2. Specimens figured as “Zamia tertiaria” by Berry (1938: pl. 9, USNM 40378h, and pl. 8, fig. 5, USNM 40378d part, respectively). Fig. 1 arrows: lower arrow indicates point expanded January 2014] WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA Soerianegara et al., 1993; Farjon et al., 1993; Farjon, 2010). The economically prized genus has been dramatically reduced from most of its lowland ranges, and many large forests that it once dominated no longer exist. Many species are still declining and are under conservation threat, in all likelihood still losing significant genetic diversity (Kitamura and Abdul Rahman, 1992). The timber is an extremely versatile, odorless softwood (Kirk, 1889; Whitmore, 1977). Exports of Agathis logs from Indonesia alone reached 760 000 m3 in a single year (1973), and a 30 000-ha forest in Kalimantan, dominated by Agathis with ca. 200 m3 timber ha–1, was completely logged out by the 1960s (Whitmore, 1977; Soerianegara et al., 1993; Farjon, 2010). The New Zealand species, A. australis, was cleared from an estimated 1.2 million ha to ca. 7500 ha coverage (>99% loss) in only ca. 50 yr (Whitmore, 1977; Farjon, 2010). Agathis microstachya (Australia) lost about half its population, and A. dammara (Malesia) has been reduced by ≥30% (Farjon, 2010). In New Caledonia, nickel mining impacts have greatly reduced Agathis populations, as well as logging (Farjon, 2010; Jaffré et al., 2010). In addition, Agathis is especially resiniferous (Salisbury, 1807), and its Manila copal was extensively tapped and dug from underground deposits (“gum-digging”) for diverse industrial uses (Kirk, 1889; Soerianegara et al., 1993; Mabberley, 2002). The remaining populations of several species have limited protection in nature reserves, but many of these are vulnerable to poaching, degazetting, clearing of surrounding buffer areas, and climate change. As adjacent lowlands are cleared and pressures from marginal tropical agriculture move upslope, the montane populations of Agathis are increasingly threatened. Agathis reproductive organs and adult foliage are notoriously difficult to sample without felling or shooting (Howcroft, 1987). They are mostly borne above long trunks that are dangerous to climb because of copious slippery resin and abscision of the lower branches. Many species are endemic to very remote or steep montane areas. Also, the large, globose seed cones shatter at maturity. Even when well sampled, there is little morphological variation among the species, such that minute technical characters of pollen cones found in the litter are usually needed to identify a giant tree (Meijer Drees, 1940; Whitmore, 1980b). As a result, detailed knowledge of morphological and genetic variation—and, thus, a solid systematic framework—have not yet been established for Agathis. Even the two most recent treatments differ substantially in species delimitations (Eckenwalder, 2009; Farjon, 2010). Fossil Agathis— The evolutionary and biogeographic history of Agathis remains poorly known from the fossil record, in sharp contrast to the outstanding, global Mesozoic and Southern Hemisphere Cenozoic fossil record of its familial relative Araucaria. There is a long history of uncertain or dubious identifications of Mesozoic and Cenozoic material to Agathis, as discussed elsewhere (Seward and Ford, 1906; Florin, 1940a; 159 Stockey, 1982; Hill, 1994; Brodribb and Hill, 1999; Hill et al., 2008; Pole, 2008). According to the most recent reviews (Hill et al., 2008; Pole, 2008), the only reliable fossil Agathis occurrences are Cenozoic and from the limited area of southern Australia, late Paleocene to early Miocene, and New Zealand, late Oligocene–Miocene. While clearly suggesting a Gondwanan origin for what is now mostly a tropical genus, nearly all these fossil occurrences are of leaf fragments with in situ cuticle or of dispersed cuticles, and several of the interpretations are contentious. Agathis tasmanica R. S. Hill and Bigwood (1987), early Oligocene of Little Rapid River and Cethana, Tasmania, is one of the few examples that convincingly preserves the complete leaf form. This includes the typical Agathis short petiole (“false petiole,” sensu Offler, 1984), the basal constriction of the blade that is not found in the other living Araucariaceae, Araucaria Juss. and Wollemia W. G. Jones et al., nor in the extinct Araucarioides Bigwood and R. Hill, which co-occurs with Agathis and Araucaria in Cenozoic sediments of Tasmania (Bigwood and Hill, 1985; Hill et al., 2008). Pole (2008) disputed some of the other Australian examples as potentially belonging to other genera. In New Zealand, abundant but isolated leaves from Newvale Mine (Oligocene–Miocene) were first assigned to Agathis sp. aff. A. australis (Lee et al., 2007) and later to Agathis sp. (Jordan et al., 2011); these were stated to lack petioles (although no leaf base was shown), which is unusual for Agathis but does occur on adult leaves of A. australis (Kirk, 1889), and to have a sharply acute apex, a feature found in few living Agathis species and not in A. australis (Offler, 1984; see also Hill et al., 2008). Moreover, Pole (2008) found the cuticular characters of the Newvale Mine fossils inconclusive. The possibility remains that the Newvale Mine fossils represent a species of Araucariaceae outside of Agathis. Regarding reproductive organs, Cookson and Duigan (1951) reported two seed cones and one pollen cone containing araucariaceous pollen, both associated with Agathis yallournensis Cookson and Duigan leaves (Oligocene–Miocene, Victoria), that they considered to be reproductive organs of A. yallournensis. Although the pollen cone did not preserve basal bracts, the remaining features are consistent with Agathis and distinct (as discussed by Cookson and Duigan) from Araucaria pollen cones also found at the site with associated Araucaria lignitici leaves. Otherwise, Agathis pollen cones have no fossil record prior to the present study, although they are the principal organs that show variation reliably at the species level (Whitmore, 1980b; Farjon, 2010) and, thus, are essential for any refined interpretation of fossils. The oldest previously illustrated fossil of a likely bract-scale unit (here, “cone scale” as widely used) dispersed from an Agathis seed cone is from the early Oligocene Cethana flora of Tasmania (Carpenter et al., 1994), although Agathis cone scales have been mentioned without illustration from the late Eocene Vegetable Creek flora, New South Wales (Hill, 1995). In New Zealand, a late Miocene cone scale and leaf base from the Oruawharo locality (Pole, 2008) ← in the inset, showing an attached leaf base with obliquely raised, darkened abscision zone; upper arrow expands to Fig. 10. 3. Spray with three abscision scars on one side of twig opposite the attached leaves, small terminal bud, and insect-feeding damage. MPEF-Pb 6303b, from quarry LH6. 4. Spray showing opposite branching, prominent grooves on twigs, numerous abscision scars with supporting tissues decurrent on the twig, well-preserved leaf bases with twisted petioles, and large, scaly terminal bud subtended by a prominent growth-increment scar. MPEF-Pb 6319, from LH25. 5. Spray showing opposite branching, two terminal buds (arrows), copious amber preserved as white, longitudinal stripes in twigs and leaves (note long distal leaf). MPEF-Pb 6313, from LH13. 6. Spray with terminal bud, weathered white. MPEF-Pb 6304b, from LH6. 7. Spray portion showing twisted leaf bases and large, scaly terminal bud. MPEF-Pb 6321a, from LH27 (also Fig. 8). 160 AMERICAN JOURNAL OF BOTANY [Vol. 101 Figs. 8–15. Agathis zamunerae sp. nov., twig features, from Laguna del Hunco except Fig. 10, from Río Pichileufú. Arrows with same orientations indicate corresponding points. 8. Detail of terminal bud shown in Fig. 7, under partial epifluorescence, showing overlapping, closely adpressed bud scales and remnant surface relief. 9. Spray portion showing small terminal bud and subtending pair of opposite leaves. Note abundant amber (white). MPEF-Pb 6312, from LH13. 10. Detail of twig at a leaf attachment point (corresponding to upper arrow in Fig. 1), showing grooved twig and leaf divergences typical for Agathis in a historical specimen. 11. Well-preserved twig with one remaining attached leaf, strong longitudinal grooves, several (sub)opposite, decussate abscision scars, swellings, and breakage scars. MPEF-Pb 6305a (left), b (right and Figs. 12–14), from LH6. 12. Detail, well-developed grooves and ridges and blanketing mesh of tiny, quadrangular epidermal cells of the former green twig. 13. Detail, grooves and epidermal cells. 14. Detail of dark, raised abscision scar supported by woody supply tissues extending from the twig. 15. Composite image (9 panels) of a grooved twig, apical direction to right, with several opposite decussate pairs of abscision scars and one attached leaf at right (three others attached to this twig are outside of frame). MPEF-Pb 6320b, from LH27. provide a more convincing, though younger example of fossil Agathis than the Newvale Mine fossils mentioned above. Given the sparse, fragmentary record, the fossils so far assigned to Agathis may or may not represent plants that had abundant features of the living genus. Based on the known fossil record exclusive to Australia and New Zealand, it has long been suggested that Agathis probably evolved in those areas (Florin, 1963:181; Gilmore and Hill, 1997; Hill and Scriven, 1998; Kunzmann, 2007). Likewise, no fossil or native living Agathis has previously been recorded from South America. The Eocene fossil sites of Patagonia are producing a large number of extant conifer, fern, and angiosperm genera that show trans-Antarctic connections to fossil and extant Australasian floras (see Materials and Methods). These occurrences January 2014] WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA 161 Figs. 16–24. Agathis zamunerae sp. nov., leaves. Note dark abscision scars with elliptical cross sections, well-defined petioles, blunt apices, range of aspect ratios, and parallel, straight venation. Figs. 17 and 23, Río Pichileufú (arrows show corresponding points), others from Laguna del Hunco. 16. Leaf with abundant coalified mesophyll. MPEF-Pb 6365, from LH13. 17. Specimen figured as “Zamia tertiaria” by Berry (1938: pl. 8, fig. 4, USNM 40378f counterpart). Note typical Agathis features listed above, plus abundant, longitudinal amber casts of the resin ducts (also Fig. 23). 18. MPEF-Pb 6363, from LH13. 19. MPEF-Pb 6374, from LH27 (also Figs. 26, 27, and 30). 20. MPEF-Pb 6359a, from LH13 (also Figs. 21 and 22). 21, 22. Details at and near base of MPEF-Pb 6359a (Fig. 20), showing constricted petiole and bifurcating veins. 23. Detail, left-margin of leaf in Fig. 17, showing resin ducts (white amber casts) alternating with veins (dark, coalified). 24. Petiole detail, showing elliptical cross section. MPEF-Pb 6334, from LH6. notably include evidence for the other two extant genera of Araucariaceae: Wollemia-type pollen (Dilwynites) has recently been discovered in the early middle Eocene Ligorio Márquez Formation in Santa Cruz Province, Argentina, although some living species of Agathis can produce similar pollen (Macphail et al., 2013; Macphail and Carpenter, 2013), and Araucaria 162 AMERICAN JOURNAL OF BOTANY [Vol. 101 Figs. 25–31. Agathis zamunerae sp. nov., fine leaf-surface features, all with long axis of leaf vertical and apex upward, Laguna del Hunco. All under epifluorescence except Fig. 27. 25. Set of parallel veins, no stomata preserved. MPEF-Pb 6386, from LH27. 26, 27. Veins with intervening rows of numerous, coalified, randomly oriented Florin rings, from leaf shown in Fig. 19 (also Fig. 30). Same approximate leaf area under epifluorescence (Fig. 26) and under reflected light to show visual cues as under a hand lens (Fig. 27), corresponding Florin rings circled. 28. As in Fig. 26, different leaf, with resin duct remains (white amber cast) and coalified mesophyll. MPEF-Pb 6322b, from LH27 (also Figs. 29 and 31). 29. Detail from leaf shown in Fig. 28 (also Fig. 31). 30. Guard cell casts preserved within coalified Florin rings, from leaf shown in Figs. 19, 26, and 27. 31. Guard cell cast, from leaf shown in Figs. 28 and 29. macrofossils have long been known from many Patagonian sites (Panti et al., 2012), including those studied here (Berry, 1938; Wilf et al., 2005). In his classic monograph on the middle Eocene Río Pichileufú flora of Río Negro Province, Argentina, Berry (1938) illustrated a number of foliar specimens, several attached to axes (Figs. 1 and 2), that he assigned to the putative cycad “Zamia” tertiaria Engelhardt (1891), a name based on a fragmentary leaf fossil from Eocene deposits in Chile. Zamia L. is an entirely New World genus. We have recovered numerous new specimens of “Zamia tertiaria” sensu Berry 1938 at Río Pichileufú and, especially, from the early Eocene Laguna del Hunco flora, where it is the seventh most abundant leaf type among >150 overall, and by far the most common gymnosperm leaf type (Wilf et al., 2005: fig. 3). The leaves also preserve a notable richness of insect-feeding damage, under separate study (C. C. Labandeira et al., unpublished data). A priori, this high relative abundance of broad fossil leaves, indicating very significant biomass (e.g., Burnham et al., 1992) and a large component community, seemed very unlikely for a presumably small cycad species within a forest of tall rainforest trees (e.g., Wilf, 2012), and it became clear from a number of features, especially the bumpy January 2014] WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA 163 Figs. 32–36. Agathis zamunerae sp. nov., (presumed) immature seed cone from Laguna del Hunco, terminal on a thickened branch, with large, transverse growth increment scar (rightward arrows). Numerous imbricate, upturned cone-scale apices are preserved across the cone base as impressions with very low but visible relief, their distal margins coalified, forming a pattern of numerous, darkened, concave-downward arcs (the margins) capping slight bulges in the matrix (the apex impressions). MPEF-Pb 6391b, from LH27. Arrows with same orientations indicate corresponding points. Fig. 35 equals Fig. 34 with colors reversed. 32. Whole specimen. 33. Detail of the area preserving cone-scale impressions/margin compressions, subtended by the growth increment scar, composite image under low-angle light. 34–36. Details of surface. twigs with well-defined terminal buds and decussate phyllotaxy, that “Z. tertiaria” sensu Berry 1938 is a conifer with simple leaves, not a compound-leaved cycad. Here, we show that “Z. tertiaria” leafy branches and isolated leaves from Eocene Patagonia (Figs. 1–31), and a suite of newly discovered, associated female and male reproductive organs (Figs. 32–72), can all be assigned to a new fossil species of Agathis. Agathis is revealed as the dominant conifer of Eocene Patagonian rainforests, where it presumably towered over many of the same taxa that it associates with today in Australasia and Southeast Asia and had equally great ecological importance. MATERIALS AND METHODS Laguna del Hunco and Río Pichileufú—The early Eocene Laguna del Hunco flora (LH, ca. 52.2 mya) and the early middle Eocene Río Pichileufú flora (RP, ca. 47.7 mya) come from northwestern Chubut and western Río Negro provinces, respectively, in northwestern Patagonia, Argentina. Locality information, maps, and stratigraphic and geochronologic data have been given in several recent papers (e.g., Wilf et al., 2003; Wilf, 2012). These classic sites were first reported in the 1920s and 1930s (Berry, 1925, 1935a, b, c, 1938) and preserve fossiliferous caldera-lake deposits within a regional volcanic province (Aragón and Romero, 1984; Aragón and Mazzoni, 1997). Paleontological and geological investigations at Laguna del Hunco and Río Pichileufú have increased greatly over the past decade. As recently reviewed (Wilf et al., 2009; Wilf, 2012): the 164 AMERICAN JOURNAL OF BOTANY [Vol. 101 Figs. 37–39. Agathis zamunerae sp. nov., cone scale with in situ seed, Laguna del Hunco. MPEF-Pb 6398, from LH13. The seed is preserved mostly as a very thin sediment cast, with some dark organic material remaining in the seed body. The rounded, larger wing (extending to distal left in this view) is broken near its apex. The rudimentary wing is clearly visible, extending to distal right (in this view) from the seed body. 37, 38. Standard image and grayscale-inverted duplicate. 39. Composite of 84 images in 44 panels, each taken with very low-angle, unidirectional lighting to show fine-scale relief features. In addition to the seed remains, note typical Agathis cone-scale features as detailed in next plate. ages are well onstrained from recent 40Ar-39Ar analyses and supplemented at Laguna del Hunco by paleomagnetic data from a 170-m stratigraphic section; the paleoenvironments were similar to those of Australasian subtropical and montane tropical rainforests; the fossil compression floras and their insect damage are among the most diverse known in the world; and a large number of novel insect taxa are present, along with fish and other vertebrate fossils. A striking biogeographic pattern emerging from recent systematic studies is the Gondwanan signature from the numerous plant taxa that are found at Laguna del Hunco, or from both Laguna del Hunco and Río Pichileufú, that are extant in Australasian rainforests and often extinct in South America. In addition, many of these elements are commonly associated with each other, and with Agathis, in their extant ranges. The long and growing list of “southern connection” examples from one or both of these floras, many of which constitute the only fossil occurrences of the respective taxon in South America, requires updating here. Ferns include Todea (Osmundaceae; extant in New Zealand, Australia, New Guinea, and southern Africa; Carvalho et al., 2013) and Dicksonia (Dicksoniaceae; Malesia, Australia, New Caledonia, New Zealand, South and Central America; Berry, 1938; Carvalho et al., 2013). Broadleaved conifers, which collectively provide the most significant evidence for a rainforest environment with a tall canopy, include Papuacedrus (Cupressaceae; New Guinea and Moluccas; Wilf et al., 2009); Araucaria section Eutacta (Australasia; Berry, 1938) and Agathis reported here; and in the Podocarpaceae, Podocarpus (global, primarily Southern Hemisphere; Berry, 1938), Dacrycarpus (Australasia and Southeast Asia; Florin, 1940a; Wilf, 2012), Acmopyle (Fiji and New Caledonia; Florin, 1940b; Wilf, 2012), and an undescribed species of Retrophyllum (Fiji, New Caledonia, Moluccas, Neotropics; Wilf, 2012). Basal (noneudicot) angiosperms include leaves of the primarily Gondwanan families Atherospermataceae and Monimiaceae that are most similar to the living Australian genera Daphnandra and Wilkiea, respectively (Berry, 1935c; Knight and Wilf, 2013). Eudicots include the iconically Australian Eucalyptus (Myrtaceae; Gandolfo et al., 2011; Hermsen et al., 2012), thought to represent colonization of volcanically deforested areas adjacent to standing rainforest; Akania (Akaniaceae, Australia; Romero and Hickey, 1976; Gandolfo et al., 1988); three species of Gymnostoma (Casuarinaceae; Malesia, Australia, Southeast Asia; Zamaloa et al., 2006); several Cunoniaceae, including fruits likely to represent Weinmannia (Andes, New Zealand, Malesia, Madagascar) and Ceratopetalum (Australia and New Guinea; Gandolfo and Hermsen, 2012); and diverse Proteaceae, including Orites (Australia, South America; González et al., 2007). It is noteworthy that no genus currently endemic to the Americas has so far been verified at Laguna del Hunco or Río Pichileufú. Several historical examples of endemics have turned out, after systematic revision, to represent taxa now extinct in South America (e.g., Austrocedrus/Libocedrus to Papuacedrus, Fitzroya to Dacrycarpus, and here Zamia to Agathis). Provenance and repositories—Material reported here mostly includes collections made during expeditions from Museo Paleontologico Egidio Feruglio (MEF, Trelew, Chubut, Argentina): to Laguna del Hunco in 1999, 2002, 2004, 2006, and 2009, from quarries LH2, LH4, LH6, LH10, LH13, LH15, LH22, LH23, LH25, and LH27, from float rocks, and from quarry AL-1, located 5 km January 2014] WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA 165 Figs. 40–51. Agathis zamunerae sp. nov., additional cone scales. Note typical Agathis features: basal scallops, large seed-depressions, concave-upward, asymmetrical seed-detachment scars, rounded upper corners, and thickened to recurved distal margins. All from Laguna del Hunco except Figs. 50 and 51, from Río Pichileufú. 40, 41. Specimens showing prominent seed depressions, detachment scars, and recurved apices. MPEF-Pb 6393 and MPEFPb 6392b, respectively, both from LH6. 42, 43. Details of seed-detachment scars for specimens shown in Figs. 40 and 41, respectively. Note preserved relief, admedially curving architecture below scar, and exmedially curving architecture above. 44. Detail of hooked left basal scallop of specimen shown in Fig. 41. 45. Specimen with deep seed depression and adjacent-ovule impression at basal right (arrow). MPEF-Pb 6397, from LH15. 46, 47. Specimen showing shallow left-basal kink and deep right-basal scallop (hooked tip broken). MPEF-Pb 6396, from LH13. 48. Specimen with deep seed depression. MPEF-Pb 6394a, from LH13. 49. Small scale, presumably from near the base or apex of its cone. MPEF-Pb 6395b, from LH13. 50, 51. BAR 4752 and BAR 4751, respectively, both from RP3. 166 AMERICAN JOURNAL OF BOTANY [Vol. 101 Figs. 52–61. Agathis zamunerae sp. nov., pollen cones. Note typical Agathis features: variably short to long peduncles, cluster of rounded, spoonshaped basal bracts, and peltate microsporophylls with thick stalks and rounded distal margins. Microsporophylls preserved in both external and lateral view, often on the same cone (e.g., Fig. 54). 52, 53. Holotype of A. zamunerae, part and counterpart, MPEF-Pb 6399a and 6399b, respectively, from LH6 (also Figs. 62 and 70–72). Note quadrangular cross section of the long peduncle (Fig. 53) and one basal bract pulled down, showing its inner surface (also January 2014] WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA south of the main section; and to Río Pichileufú in 2002 and 2005, from quarry RP3 and near quarry RP1, all as described in earlier studies (Wilf et al., 2003, 2005, 2009; Gandolfo et al., 2011; Wilf, 2012). The Laguna del Hunco collections from these field seasons are curated at MEF (repository prefix MPEF-Pb), and the Río Pichileufú specimens are curated at Museo de Paleontología de Bariloche (BAR), San Carlos de Bariloche, Río Negro, Argentina; letter suffixes (a, b) indicate parts and counterparts. A few additional specimens from Río Pichileufú were found in older collections at BAR. Also, we examined the historical collections of “Zamia tertiaria” from Río Pichileufú (Berry, 1938) that were collected and sent to Berry by J. R. Guiñazu, exact quarry sites unknown. This included previously uncited and unfigured cohort material as well as the figured specimens, all housed at the National Museum of Natural History, Smithsonian Institution (USNM). The small type and cohort collections from Laguna del Hunco (Berry, 1925), also located at USNM, consist entirely of angiosperm remains and, thus, are not relevant to the present study. The total collection presented here as protologue for a new species contains 154 elements: 1 twig, 36 leafy twigs, 86 isolated leaves, 1 immature seed cone, 10 seed-cone scales (1 of these with an in situ seed), and 20 pollen cones. Nearly all the fertile material is from Laguna del Hunco, which has much better preservation, but we also found three cone scales at Río Pichileufú. The new species is most common in the uppermost well-sampled level at LH (quarries LH6, 22, 25, and 27; 47% of total specimens). Fossil preparation and imaging—Techniques, software, locations, and equipment for fossil preparation, macro- and microphotography, epifluorescence microphotography, and image compositing and processing at MEF and the Penn State University Paleobotany Laboratory are the same as those reported in the recent, preceding paper on fossil conifers from these sites (Wilf, 2012), with the following minor technical notes. First, in addition to the PaleoAro and Micro-Jack #2 air scribes listed previously (Wilf, 2012), we also used the more powerful ME-9100 for fossil preparation when needed (all from Paleotools, Brigham City, Utah, USA). Second, very low-angle, unidirectional light was often used to bring out fine surface features, especially for pollen cones and cone scales; image contrast was usually set high, and some image colors were inverted (Figs. 35 and 38) to make important fine features of the fossils more visible. Third, for some epifluorescence imaging of specimens that showed low excitation response and required long exposures, a small amount of normal reflected light was sometimes allowed to mix into the exposure along with the fluorescence, with good results that better showed surface textures in combination with the dimly fluorescing features (e.g., Fig. 8, “partial epifluorescence”). All photographs are by P.W., except Figures 49–51 (I.H.E.). Field photographs in Borneo were taken on a Sony DSC-RX100 compact camera. Cuticle was usually coalified, with remnants of epidermal cells sometimes visible under epifluorescence. Only two leaf specimens preserved traces of stomatal apparati preserved as coalified Florin rings, some with guard-cell casts (e.g., Figs. 30 and 31). Extant material and characters—Herbarium collections of Agathis, comprising most of the living species, were examined by P.W. at the U.S. National Herbarium, Smithsonian Institution, Washington, D.C. (US); the Australian National Herbarium, Canberra (CANB); the National Herbarium of New South Wales, Royal Botanic Gardens, Sydney (NSW); and Royal Botanic Gardens, Kew (K). In addition, P.W. and R.M.K. examined wild Agathis trees extensively in the field, in the Atherton Tablelands region of Queensland, Australia, in August 2010 (A. atropurpurea, A. microstachya, and A. robusta), and on and around Mount Kinabalu in northern Borneo, Sabah, Malaysia, in September 2012 (A. borneensis, A. kinabaluensis, and A. lenticula). Collectively, the authors have examined all living species of Araucariaceae in herbaria, in the field, and/or in cultivation. Although it is an easily recognized genus, the species-level taxonomy of Agathis remains contentious, as seen in the large number of disagreements among the principal modern treatments (de Laubenfels, 1972, 1988; Whitmore, 1980b; 167 Eckenwalder, 2009; Farjon, 2010). Moreover, even agreed-upon names can incorporate varying sets of synonymized taxa and reference specimens and, thus, are not consistent in practical use. Here, we use Farjon’s (2010) treatment because of its relatively detailed coverage of reproductive morphology; unless otherwise noted, Farjon (2010) is the source of all nomenclature and measurements of extant conifer species mentioned below. However, all descriptions and comments made in the principal treatments cited above were tabulated and also used in the comparisons, if it was possible to adjust for synonymies. A general comparative summary of principal measurements and character states for the new fossil species, and for the extant species as described by Farjon (2010), is given in Table 1 (for additional comparisons, see Description and Discussion). As would be expected from the unsettled species-level taxonomy and generally poor genetic sampling of Agathis, there is no robust systematic framework of all the species into which to place the fossils, and no phylogenetic analysis was attempted here. Numerous recent papers have produced variable results for relationships within Agathis (e.g., Gilmore and Hill, 1997; Setoguchi et al., 1998; Stefanović et al., 1998; Conran et al., 2000; Quinn et al., 2002; Stöckler et al., 2002; Rai et al., 2008; Liu et al., 2009; Biffin et al., 2010; Leslie et al., 2012; Escapa and Catalano, 2013). Critically, the living species that we found to have greatest morphological similarity to the fossils (A. lenticula; see Discussion) has never been analyzed in a phylogenetic context with either morphological or molecular data. Thirteen (the maximum to date) Agathis species were included in a recent molecular analysis as part of a large-scale study of all conifer groups (Leslie et al., 2012). This showed Wollemia as sister to Agathis, Agathis australis of New Zealand as sister to all other sampled Agathis species, a clade containing the New Caledonian species, and a clade containing the three Australian species (A. atropurpurea, A. microstachya, and A. robusta; Hyland, 1977) that is sister to the remaining West Pacific-Asian tropical species. The distinct position of A. australis and the consistency of the New Caledonian clade appear to be robust in other studies (e.g., Escapa and Catalano, 2013), and the status of Wollemia as sister to Agathis, and of both together as sister to Araucaria, is the prevailing result from many molecular analyses (Gilmore and Hill, 1997; Stefanović et al., 1998; Conran et al., 2000; Quinn et al., 2002; Rai et al., 2008; Liu et al., 2009; Biffin et al., 2010; Escapa and Catalano, 2013). To evaluate the phylogenetic position of this and other fossil species of Agathis, the previously developed morphological matrix of Escapa and Catalano (2013) needs to be expanded to include additional living species and detailed characters of microsporophyll morphology. SYSTEMATICS AND RESULTS Family— Araucariaceae J. B. Henkel & W. Hochstetter, Synopsis der Nadelhölzer: xvii (1865), nom. cons. Genus— Agathis R. A. Salisbury, Transactions of the Linnean Society of London 8: 311 (1807), nom. cons. Species— Agathis zamunerae Wilf, sp. nov. Coniferales, morphotypes TY010 “Zamia” tertiaria, “TY012 “Araucariaceae pollen cone” (part), and TY014 “Araucaria wide cone scale” (Wilf et al., 2005: A6). Zamia tertiaria Engelhardt, Geological Society of America Special Paper 12: 57 (1938), cited Río Pichileufú material only. Etymology— In memory of the life and work of Dra. Alba B. Zamuner, 1959–2012, paleobotanist and valued colleague (see Iglesias, 2013). ← Fig. 62). Fig. 52 arrows: thin arrow corresponds to same in Figs. 70 and 71; thick arrow corresponds to same in Fig. 72. 54. Specimen with short peduncle and exposed cone axis. MPEF-Pb 6403a, from LH13 (also Fig. 66). 55. Specimen with long peduncle and well-preserved bract cluster. MPEF-Pb 6402, from LH13 (also Figs. 63–65). 56. MPEF-Pb 6409a, from LH25. 57. Specimen exhibiting cone axis and numerous individual microsporophylls in lateral view, showing thick, reflexed stalks and peltate heads. MPEF-Pb 6405a, from LH15. 58. Specimen with short peduncle and exposed cone axis. MPEF-Pb 6408b, from LH25. 59. Specimen with tightly adpressed basal bracts and exposed cone axis. MPEF-Pb 6401b, from LH13. 60. Specimen with compressed microsporophylls (dark, coaly areas) and underlying impressions exposed at right. MPEF-Pb 6406a, from LH25. 61. Elongate specimen with short peduncle and exposed cone axis. MPEF-Pb 6404, from LH15 (also Fig. 67). 168 AMERICAN JOURNAL OF BOTANY [Vol. 101 Figs. 62–72. Agathis zamunerae sp. nov., fine features of pollen cones and microsporophylls. Figs. 62–66, 68, 69, and 72 under epifluorescence. 62. Base of the holotype (Fig. 52; also Figs. 70–72), showing resin ducts in peduncle, basal bract cluster with rightmost bract pulled down, and basal microsporophylls in lateral view. 63–65. Details of cone shown in Fig. 55. Fig. 63, basal bract cluster. Figs. 64 and 65, microsporophyll heads in external view; note obscuration of the bases by neighboring heads and convexity, rounded apices, and lack of marginal denticulations. 66, 67. Cone axes in longitudinal view. Fig. 66, set of closely spaced, longitudinally elongate depressions where microsporophyll stalks detached. Counterpart of cone shown in Fig. 54. Fig. 67, basal remnants on the axis where stalks broke near the base and did not detach cleanly, and departing attached stalks to left, from cone shown in Fig. 61. 68, 69. Cone (naturally) broken obliquely, showing microsporophyll stalks and heads in oblique-dorsal view, MPEF-Pb 6313, from LH13. Note large resin ducts, thick stalks that expand distally, and (especially in Fig. 69) markedly convex, apically and basally recurved heads. 70–72. Details of microsporophylls and pollen sacs preserved in lateral view on right margin of the holotype (Figs. 52 and 62). Thin arrows indicate corresponding points in Figs. 52, 70, and 71. Thick arrow in Fig. 72 corresponds to same in Fig. 52, in same relative orientation (image here rotated counterclockwise to fit the layout). Fig. 70, set of sporophylls with light brown pollen sac clusters preserved abaxial to each stalk. Fig. 71, detail of expanding stalk termination with adaxial ridge, striated surface, and abrupt insertion into the peltate head. Fig. 72, detail, set of elongate pollen sacs, abaxial and subparallel to the dark stalk vertical at frame left. Note curving tip of the sac at lower right; the tip is lying free on the rock surface. Composite of 68 images in 9 panels. January 2014] WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA Holotype— MPEF-Pb 6399 (Figs. 52, 53, 70–72), a pollen cone part and counterpart from Laguna del Hunco, Tufolitas Laguna del Hunco, early Eocene, Chubut Province, Argentina, quarry LH6 of Wilf et al. (2003). Paratypes— Laguna del Hunco, Tufolitas Laguna del Hunco, early Eocene, Chubut Province, Argentina. Twig: MPEF-Pb 6301 (quarry LH13). Leafy twigs: MPEF-Pb 6302 (LH2); 6303–6306 (LH6); 6307 (LH10); 6308–6315 (LH13; 6313 also with unattached pollen cone); 6316–6318 (LH22); 6319, 6422 (LH25); 6320–6323, 6423 (LH27); 6324 (float). Leaves (isolated): MPEF-Pb 6325 (AL1); 6326, 6327 (LH2); 6328–6330 (LH4); 6331 (level of LH4); 3160, 6332–6342, 6344–6348 (LH6); 6349 (LH10); 6350–6367 (LH13); 6368 (LH23); 6369– 6373 (LH25); 6374–6388, 6420, 6421 (LH27); 6389, 6390 (float). Seed cone: MPEF-Pb 6391 (LH27). Cone scales: MPEFPb 6392, 6393 (LH6); 6394–6396 (LH13); 6397 (LH15). Cone scale with attached seed: MPEF-Pb 6398 (LH13). Pollen cones: MPEF-Pb 6313 (LH13, on block with leafy twigs per above); 6400 (LH6); 6401–6403 (LH13); 6404, 6405 (LH15); 6406– 6409 (LH25); 6410–6417 (LH27). Río Pichileufú, La Huitrera Formation, early middle Eocene, Río Negro Province, Argentina. 1. Original, historical collection, exact quarry sites unknown, figured material referred to “Zamia” tertiaria Engelhardt by Berry (1938). Leafy twigs: USNM 40378c, 40378d, 40378h (Berry 1938: pls. 8.2, 8.5, and 9, respectively). Leaves (isolated): USNM 40378e, 40378f, 40378g (Berry 1938: pls. 8.1, 8.4, and 8.3, respectively). 2. Additional cohort material from the historical collection, not previously reported, identified as “Zamia tertiaria” on Berry’s handwritten tags. Leafy twig(s): USNM 545227, 545230, 545235. Leaves (isolated): USNM 545223–545226, 545228, 545229, 545231– 545234, 545236–545238. 3. Older BAR collections. Leafy twig(s): BAR 288-20, 1214-20, 5002-20. Leaves (isolated): BAR 1211-20, 1214-20. 4. Recent collections for current project. Leafy twigs: BAR 4748 (near RP1), 4749 (RP3). Leaf (isolated): BAR 4750. Cone scales: BAR 4751–4753. Specific diagnosis—Leaves with consistently elliptic to lanceolate shape; long length (to ≥132 mm); and a generally high length:width ratio (observed 3.9–11.5:1). Seed body ca. 12 × 7 mm, and larger seed wing ca. 13 × 8 mm. Pollen cones with stout, short to long peduncle (to ≥7.3 mm); relatively few basal bract pairs (3 pairs observed), arranged in a tightly imbricate cluster with width less than that of the cone body (sporophyll-bearing region) and no elongated bracts; cylindrical to slightly convex cone body with long length (to ≥56 mm); and imbricate microsporophylls with head width ≤2 mm and entire distal head margins. Description—Resin, preserved as amber, abundant in all organs. Twigs (Figs. 1–15) opposite, strongly grooved longitudinally, with quadrangular epidermal cells sometimes present (on presumed green twigs in life) and obliquely exserted leaf-abscision scars subtended by woody supply tissues that are long-decurrent on the axis. Terminal bud conspicuously globose, with many tightly imbricate bud scales. Leaves (Figs. 1–7, 9–11, and 15–31) well separated along the twig, opposite to subopposite decussate, deployed distichously via basal twisting of the narrow petiole. Petioles elliptical in cross section (e.g., Fig. 24), width at base 1.2–4.2 mm (mean ± 1 SD = 2.3 ± 0.8 mm; N = 51), darkened in distinct abscision zone. Blades symmetrical, elliptical to lanceolate, the widest portion occurring at 35–63% of the total blade length (48 ± 6%, N = 52), the base and apex acute, the apex 169 slightly rounded or blunted, never sharp-pointed, not acuminate or falcate. Blade length 24.3–132.4 mm (66.7 ± 17.1 mm, N = 59), width 5.7–18.5 mm (10.6 ± 2.7 mm, N = 94), length:width ratio 3.9–11.5:1 (6.6 ± 1.7, N = 53). Blade dimensions vary continuously among samples, such that no clear recognition of juvenile versus adult foliage is possible. Veins parallel, midvein absent, course nearly straight and little influenced by margin curvature, and numerous, via dichotomies from the petiolar veins (Fig. 22). Resin ducts alternate with the veins (Fig. 23; see Kausik, 1976). Stomata (Figs. 25–31) rarely preserved but numerous and densely packed wherever observed, usually in two rows per vein, randomly oriented (oblique, perpendicular, or parallel to the veins), preserved as casts of guard cells and/or as coalifed Florin ring compressions of maximum long-axis length ca. 65 μm. Amphistomy, variation in stomatal distribution or size along the leaf length, and variation in the length or continuity of stomatal strips (Kausik, 1976) could not be confidently discerned. Immature seed cone (one specimen, Figs. 32–36) ovate, length 34 mm, width 33 mm, terminal on a thickened branch (width 21 mm) that has a prominent growth-increment scar. Cone scales (ovuliferous bract-scales) helically arranged in the cone, their apices upturned in smooth arcs, without spiny distal projections. When preserved separately (Figs. 37–51), presumably as mature, dispersed units, cone scales as wide as or wider than long, length 18.6–26.1 mm (22.9 ± 2.2 mm, N = 9), width 21.4–35.7 mm (27.7 ± 4.9 mm, N = 9), distal margins thickened and upturned or recurved, the apex broad and slightly expanded, with either an attached seed (Figs. 37–39) or with a narrow, elliptical seed depression and an asymmetrically curved, distally concave seed-detachment scar (Figs. 40–43). An impression of the adjacent ovule in the cone may be present (Fig. 45). Longitudinal architecture (fibers, resin ducts, vasculature) within the seed depression area oriented more linearly than outside, converging slightly admedially into the detachment scar, then curving exmedially in the area distal to the scar (Figs. 42 and 43). Cone-scale base scalloped (auriculate) on both sides where preserved, usually hooked to a sharp point on at least one side, sometimes reduced to a kink on other side, the scallops incised 1.1–5.2 mm from the base and without frilly projections. Cone scale upper corners rounded, the distal margin smooth, straight to rounded, thickened to recurved, and with a slight, broad distal expansion in the center. Pollen tubes not preserved (see Kaur and Bhatnagar, 1986). Seed (one specimen, Figs. 37–39) at center of the cone scale base, single, inverted, and ovoid, length ca. 11.8 mm, width ca. 7 mm, its long axis aligned to that of the scale, its body protruding slightly below the scale basal margin, with two opposite wings: one large and well-rounded apically, directed at ca. 40° in relation to the left basal margin (in adaxial view as preserved and shown), length ca. 13.4 mm, and one small, rudimentary, length ca. 3 mm, with an acute, pointed apex. Pollen cones (Figs. 52–72) cylindrical to slightly convexsided, inserted on a stout peduncle, with subtending bract clusters, apex smoothly curved. Peduncles short to long, straight-sided to semiconical, rounded to quadrangular (Fig. 53) in cross section, expanding distally to the approximate width of the cone bracts, distally concave upward. Peduncle length 2.2–7.3 mm (4.3 ± 1.6 mm, N = 7), minimum width 1.0– 3.5 mm (2.8 ± 0.8 mm, N = 8), maximum width 4.1–6.8 mm (5.6 ± 0.8 mm, N = 13). Cone length, including bracts but not peduncle, 23–56 mm (40.0 ± 9.5 mm, N = 10), diameter 6.6–10.8 mm (7.7 ± 1.2 mm, N = 16). Bracts tightly imbricate, apparently consistently in three pairs, ovate, apices rounded, forming a cluster 4.7–8.4 mm wide (6.1 ± 1.0 mm, N = 13) that is 68–97% 170 AMERICAN JOURNAL OF BOTANY [Vol. 101 Figs. 73–81. Extant Agathis, selected features of dried material for comparison to fossils. All except Fig. 77 are litter samples of a cultivated A. robusta, Myocum, New South Wales, Australia. Figs. 76 and 80 under epifluorescence. 73. Twigs with terminal buds of varying sizes. Note marked longitudinal striations, prominently and obliquely raised abscision scars with decurrent supporting tissue, and scaly, rounded buds. Compare Figs. 1–15. 74. Detail of a large terminal bud, showing numerous overlapping scales and crowded, subtending abscision scars. Compare Fig. 8. 75, 76. Twig closeup showing longitudinal ridges and grooves and quadrangular epidermal cells. Compare Figs. 12 and 13. 77. Seed-cone base, Agathis macrophylla (Aneityum Island, Vanuatu, S.F. Kajewski 760, US Fruit Collection 325). Note thickened fertile branch and large growth-increment scar subtending the cone, and imbricate, upturned scale tips with rounded, convex-upward margins. Compare Figs. 32–36. 78. Distal left corner (in adaxial view) of seed-abscision area of a cone January 2014] WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA the width of the sporophyll-bearing region of the cone (80.3 ± 9.3%, N = 12) and is fully constrained below the first microsporophylls, with no elongate or leaflike basal bracts present. Bract length 2.4–4.7 mm (3.5 ± 0.5 mm, N = 8), width 2.3–3.5 mm (2.8 ± 0.5 mm, N = 7). Microsporophylls (Figs. 67–72) imbricate, peltate, numerous (ca. 250–500 cone–1), helically arranged. Stalks striated and with an adaxial median ridge, reflexed basally to accommodate mass of the head and pollen sacs, where detached leaving irregular pits (if cleanly detached, Fig. 66) or basal remnants (Fig. 67) on the cone axis. Stalk length 1.9–2.9 mm (2.4 ± 0.4 mm, largest values from 11 cones), stalk plus head total length 2.4–3.7 mm (3.0 ± 0.5, from 11 cones). Stalk and its median ridge expand distally (Figs. 69–71), before their peltate insertion into most of the microsporophyll head. Heads (Figs. 64, 65, and 68–71) abruptly angled from the stalks, then strongly recurved apically and deeply basally, outwardly markedly convex, the shape ovate, the margin and apex smoothly rounded and without angled tips, notches, serrations, or denticulations. In external view (e.g., Figs. 64 and 65), the basal margins of the heads are obscured by imbrication. Head height in external view 1.5–2.1 mm (1.7 ± 0.2 mm, from 12 cones), width 1.3–2.0 mm (1.6 ± 0.3 mm, from 13 cones). Pollen sacs (Figs. 70 and 72) apparently immature where observed, attached to the inner abaxial portion of the microsporophyll head, preserved as light brown patches, each containing several narrow, elongate sacs, the sac outlines subparallel to the microsporophyll stalks; number of sacs could not be determined with confidence; pollen not preserved. Remarks— We designate a pollen cone as the holotype for the new species because it is well recognized that pollen cones are the only organs of the genus Agathis that have relatively abundant and distinctive characters at species level, once the generic diagnosis is made from all available material (e.g., Whitmore, 1980b; Farjon, 2010). The holotype was collected 6 December 2002 (by P.W., K.R.J., and crew). We refer all the cited fossil-plant organs to a single species because there is no evidence that more than one taxon is definably present. There are also no differences yet apparent among samples from the two sites (L.H. and R.P.), despite intensive sampling of their bulk floras. Moreover, each organ type recovered is independently assignable to Agathis using most of the standard botanical characters for the genus (see Familial and generic affinities) and exhibits a self-consistent set of features and dimensions, and the various organs are all found very closely associated on single bedding surfaces. The certain attachments include the 36 specimens of twigs with attached leaves (e.g., Figs. 1–7) and one seed in place on a cone scale (Figs. 37–39). DISCUSSION The Zamia tertiaria problem—“Zamia” tertiaria Engelhardt (1891:646 and pl. 2 [Fig. 16]) is based on the single, holotype 171 foliage specimen from the Eocene of Coronel, Chile, which is now apparently lost, along with most other material from Engelhardt’s important 1891 monograph (Wilf, 2012). Engelhardt’s drawing shows a parallel-veined leaf or leaflet with curved margins and no clear base or apex. Engelhardt further described this foliage as pinnate, leathery, and sessile, without illustration of these traits. Little can be said here to affirm or reject the identification to Zamia, especially with the holotype unavailable. Thus, Engelhardt’s “Z.” tertiaria from Chile cannot be linked in any meaningful way to the specimens described here from Argentina, nor to Agathis. Much later, Berry (1922:120 and pl. 1 [Fig. 4], pl. 2 [Figs. 1–3]) assigned several Eocene foliar specimens that he collected from Arauco Mine, Curanilahue, Chile, to “Z.” tertiaria Engelhardt. He also claimed that several specimens, including one figured specimen (his pl. 1 [Fig. 4]), showed attachment to a rachis “imbedded in the matrix.” Berry’s figured specimens survive (USNM 320640–43, not shown), and on examination they are somewhat different from his drawings and show typical monocot features, including at least two orders of parallel veins (i.e., A and B veins sensu Hickey and Peterson (1978), and distinct plications along the A veins, best seen in USNM 320643). There is no evidence of attachment to a rachis. Berry (1922) also assigned to “Z. tertiaria” a second specimen from Engelhardt’s monograph that Engelhardt (1891: pl. 1 [Fig. 4]) had identified as a monocot leaf fossil (“Monokotyler Blattrest”). On the basis of Engelhardt’s illustration, the only information available, this specimen was quite different from the “Z.” tertiaria holotype, and in fact very monocot-like, in having many more parallel veins, numerous cross veins, and a much more elongate, strap-shaped aspect. It is possible that Engelhardt’s “Monokotyler Blattrest” was indeed related to the material from Arauco that Berry assigned to “Z. tertiaria,” but not in the way Berry thought (all monocots, vs. all cycads per Berry). In any case, Berry’s (1922) “Zamia tertiaria” specimens show no affinity to Engelhardt’s (1891) “Zamia” tertiaria, as suggested long ago by Hollick (1932), nor to conifers. However, of historical note, Hollick (1932:177) explicitly noted a general similarity of Berry’s (1922) specimens (probable monocots) to Agathis. Subsequently, Berry (1938) referred specimens from Río Pichileufú to “Zamia” tertiaria Engelhardt (e.g., Figs. 1, 2, and 17; see also Familial and generic affinities), and these, including Berry’s previously unreported cohort material, are the only historical specimens of “Zamia” tertiaria that are reassigned here to Agathis zamunerae. Berry’s Río Pichileufú material is quite distinct from all the Chilean entities discussed above, excepting perhaps the lost, fragmentary holotype of “Z.” tertiaria. Even if this specimen were found and determined to have features of Agathis, it would still lack the large suite of characters, including those of leaf attachment and female and male reproductive organs, that is preserved in A. zamunerae. In summary, ← scale. Note strong relief, incurved architecture immediately basal to the scar, and outwardly curved architecture immediately distal to the scar. Compare Figs. 42 and 43. 79–81. Pollen cone with upward-facing microsporophylls removed manually, remaining microsporophylls in approximate lateral view as in several of the fossils. Fig. 79 shows large pits on the cone axis where the enlarged microsporophyll bases had inserted and from which they detached completely (cf. Fig. 66), as well as some remnants where the stalks broke off near the base (cf. Fig. 67). Epifluorescence in Fig. 80 clearly distinguishes tissues of the stalks (note striations and adaxial ridges as in the fossils), the abaxial pollen sacs, and the peltate, convex, apically and deeply basally recurved heads (cf. Figs. 69–72). Fig. 81, Single microsporophyll (compare Figs. 69–72). Note enlarged base, prominent, distally enlarged adaxial ridge, and the distinct tissues of the head and the pollen sacs, which have dehisced, in contrast to those in the fossils (Fig. 72). 172 AMERICAN JOURNAL OF BOTANY [Vol. 101 Figs. 82–88. Agathis lenticula in Kinabalu National Park and environs, Sabah, Malaysian Borneo, September 2012. 82. Large emergent tree, lower Mesilau Trail. 83. Young shoot, lower Mesilau Trail, showing typical Agathis features: green twig, opposite-decussate leaf attachment, distichous leaf deployment via basal twisting of petioles, parallel venation, and rounded terminal bud. Compare, e.g., Figs. 1–7. The lens-shaped juvenile leaves are typical for this living species (and not the fossils). 84. Litter sample from below large tree, bank of Mesilau River. Note raised, opposite-decussate abscision scars on twigs with decurrent supporting tissues (compare Figs. 11, 14, and 15), petioles with abscision scars on the leaves (compare Figs. 16–21 and 24), and pollen cone fragments. 85. Litter sample of pollen cones, from large tree below Kiau View trailhead. Note numerous similarities to the fossils: tightly adpressed basal bracts with width less than that of the full cone, variably short to long and quadrangular (second from left) peduncles, cylindrical to convex cone shape, and imbricate, convex microsporophyll heads (compare Figs. 52–72). Each small scale tick = 1 mm. 86, 87. Cone scales in litter below large tree, Mempening Trail, with (Fig. 86) and without (Fig. 87) the seed still in place. Note typical Agathis features: hooked basal scallops, rounded apical January 2014] WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA “Zamia” tertiaria Engelhardt is an unsuitable basionym for the Agathis fossils reported here, thus requiring the new species. Of additional historical interest, Petersen (1946:49), referring to Berry (1938), made the first record of “Zamia tertiaria” Engelhardt at Laguna del Hunco as part of his outstanding geological survey of the middle Chubut River region. Although Petersen’s collections are apparently lost, it is reasonable to infer that his identification (sensu Berry, 1938) was probably correct, and therefore that Petersen was the first scientist known to collect what is here designated as Agathis zamunerae, at its type locality. Familial and generic affinities— Each of the preserved organs of the new species displays a large number of distinctive features that, in combination and often singly, are only found in Agathis. These characters include most of those used by botanists to identify living Agathis and its species. Pending confirmation from a phylogenetic analysis, which would require much more data from the extant species, we conclude from the wealth of preserved morphological data that Agathis zamunerae sp. nov. is, in all probability, closely related to the living species of Agathis and belongs at least in the crown of the genus, and perhaps in a derived position therein. A selection of comparative details from extant live, litter, and dried material is shown in Figures 73–87. Beginning with vegetative features: conspicuously grooved, stout “green” twigs with globose, scaly terminal buds, bearing opposite to subopposite, decussate, distichously deployed, simple, symmetrical, well-separated, multiveined, straight-veined leaves with narrow petioles, a blunt apex, and randomly oriented stomata with Florin rings, are, collectively, firmly diagnostic of Agathis. Wollemia and some Araucaria species also have multiveined leaves, but these are sessile (and decurrent in Wollemia), overlap densely along the twig, lack conspicuous Florin rings, and have more longitudinally oriented stomata in most species (Florin, 1931; Cookson and Duigan, 1951; Stockey and Taylor, 1981; Stockey, 1982; Bigwood and Hill, 1985; Stockey and Atkinson, 1993; Chambers et al., 1998; Burrows and Bullock, 1999; Hill et al., 2008; Pole, 2008; Escapa and Catalano, 2013). Araucaria foliage is helically arranged, not decussate nor distichously deployed, and nearly always with a sharp apex; Wollemia leaves are distichous to four-ranked and trimorphic. Araucaria pichileufensis Berry (1938) foliage, which occurs abundantly at the same fossil localities at Laguna del Hunco and Río Pichileufú, is easily recognized as distinct from Agathis zamunerae in having the typically narrow, short, single-veined, imbricate, helically deployed leaves of Araucaria Section Eutacta. Outside Araucariaceae, the only living genus with vegetative features similar to Agathis (including A. zamunerae), especially in often having opposite–subopposite, elliptic, well-spaced, petiolate, multiveined leaves, is Nageia (Podocarpaceae). However, this genus has a completely different, podocarpaceous-type, 173 acute terminal bud and veins that much more noticeably curve with the margin and recurve toward the apex; both these features are used to distinguish living Nageia from Agathis where they co-occur (Sterling, 1958; de Laubenfels, 1988; Beaman and Beaman, 1993). In addition, Nageia, like most podocarps and unlike A. zamunerae, has longitudinally oriented stomata (Florin, 1931; Hill and Pole, 1992). We note that broad, multiveined conifer leaves that are generally similar to our vegetative fossils are abundant throughout the Mesozoic and early Cenozoic and attributed to various conifer lineages (e.g., Heidiphyllum, Nageiopsis, Podozamites, Araucarioides (see Axsmith et al., 1998; Hill et al., 2008; Miller and Hickey, 2010), but the full combination of leaf and twig features preserved here is characteristic only of Agathis. Although the new material cited here from Río Pichileufú shows abundant Agathis twig and leaf features and includes associated cone scales (Figs. 50 and 51), it would be difficult to fully refute Berry’s (1938) assignment of his original suite of vegetative specimens from that site, considered alone, to Zamia without the strong corroboration from these new fossils. There are indeed many relevant similarities between some Zamia leaves and Agathis leafy branches, including grooved twigs/rachises, petioles/narrow leaflet bases, leaf(let) articulation and/or abscision, elongate and narrow leaves/leaflets, and parallel venation. However, even Berry’s specimens show features not found in Zamia, nor any cycads to our knowledge: the twigs are notably bumpy and include expanded support tissue under the obliquely raised abscision zones (e.g., Figs. 1, 2, and 10); leaf attachment is decussate (e.g., Fig. 2); and the leaves have copious resin and thick abscision zones that would be very unlikely in Zamia (Figs. 17 and 23). The Zamia problem aside, special care must be taken when identifying foliage with parallel venation at the two fossil sites, because of the presence of monocots and because of two other parallel-veined gymnosperm taxa, which, along with the conifers listed earlier (see Materials and Methods), complete the gymnosperm flora so far known. First, Ginkgo patagonica Berry (1935b) can quickly be distinguished from Agathis because it is palmately lobed and is usually preserved with thick, abundant cuticle unlike any Agathis studied here; however, the lobe tips can be confused with Agathis if found isolated and without cuticle. Second, we have recently found fossils of a true cycad at Laguna del Hunco (Wilf et al., 2003: fig. 1I). These have petiolulate, long leaflets with parallel venation that are much like Agathis, but the leaflets are toothed with decurrent bases and lack articulations or abscision zones. Preliminary indications are that this cycad closely resembles the African genus Encephalartos (P. Wilf, unpublished data). The female reproductive features described here are also stereotypical for Agathis. As in all Araucariaceae, the cone (Figs. 32–36), though not well preserved, arises on a thickened branch, is large and rounded (here subround due to presumed immaturity), and has flattened, densely and helically arranged cone scales with ← corners, and thickened, recurved, nonprojecting apex of the scale; large, ovoid seed body and corresponding depression in the scale; lateral impressions of adjacent seed bodies; presence of one enlarged, broadly curved wing extending at an angle distally and to right (in this view) and one rudimentary wing to left (individual cones may be “right-handed” or “left-handed;” this does not appear to have taxonomic significance), and corresponding impressions and discoloration of the scale; and small, curved seed-abscision zone. Compare Figs. 37–51. 88. A large area east of the park’s Mesilau entrance that was recently degazetted, deforested, and planted for a cabbage monoculture, requiring intensive pesticide use. The cleared landscape is dense with large stumps. Remaining intact, primary montane rainforest of the main body of the park, containing numerous, large Agathis lenticula and Dacrycarpus kinabaluensis in this area, is in the background. The current park boundary is several tens of meters behind the forest line visible on the green slopes. Inset, stump of a felled Agathis from this unprotected strip and its exuded copal. 174 AMERICAN JOURNAL OF BOTANY upturned tips. However, the large, prominently visible growthincrement scar subtending the fossil cone (see Fig. 77), the lack of well-developed subtending foliage (or any foliage in this case), and the lack of spinose or elongate cone-scale tips are collectively typical for Agathis and not for Araucaria or Wollemia (de Laubenfels, 1972; Jones et al., 1995). An important feature of Agathis cone scales that is easily seen in the isolated fossil scales is the marked basal scallops (e.g., Figs. 44, 47, 86, and 87), which function in life to provide accommodation space for the seeds of adjacent scales within the tightly packed seed cone. These are not present in Araucaria and, likewise, are not seen in the cone scales of the cooccurring A. pichileufensis. Wollemia cone scales have basal embayments, but these are broader than in Agathis, and the overall scale shape is markedly rhombic, unlike in Agathis and the fossils. Further, as just mentioned, the cone scales of Araucaria, including A. pichileufensis, and Wollemia typically have triangular to spinose, projecting tips (especially in Wollemia; Jones et al., 1995) that comprise the ovuliferous scale portion that is free of the bract, whereas in Agathis (excepting A. australis) and the fossils, there is consistently no apical projection, or only a very broad, blunt expansion (e.g., Fig. 40), and the bract and scale components appear to be fully fused. We also note that Dettmann et al. (2012: table 2) reviewed the best-preserved fossil seed-cone taxa of Araucariaceae, all of them Mesozoic, and none of these has scalloped (“auriculate”) cone scale bases as in Agathis, nor petiolate, opposite associated leaves. All Araucariaceae have a single, inverted seed per cone scale, as in the fossils. However, the seeds of Agathis and its sister Wollemia are adpressed but attached to the scale only by a weak stalk from which they are usually, though not always, shed, leaving on the scale a characteristic, rhomboidal (Wollemia) or asymmetrical curved (Agathis and fossils) abscision scar and a marked, longitudinally grooved seed depression, as seen in the fossils (e.g., Figs. 40–43, 45, 46, and 48; Owens et al., 1997; Chambers et al., 1998; Dettmann et al., 2012). In Araucaria, including A. pichileufensis from the same fossil localities, the seed is embedded in the tissues of the cone scale. The fossil seed in situ on its cone scale (Figs. 37–39), preserved extremely fortuitously and mostly as a very thin sediment cast, clearly shows typical Agathis positioning and morphology, including an ovoid body that projects slightly below the scale base, a concave-upward detachment area, and two, strongly asymmetrical wings, this asymmetry being a recognized synapomorphy for the genus (Escapa and Catalano, 2013). Wollemia has a single, relatively narrow wing that surrounds its seed and does not resemble the fossil. We note for general interest that DiMichele et al. (2001) reported an Early Permian gymnosperm seed with unequal wings that looks surprisingly similar to Agathis, although the wing architecture is quite different. The fossil pollen cones exhibit several features that are distinctive for Agathis. Most notably, the peduncle is well defined and can be elongate, and the basal bracts are broad, smoothly rounded, and contained below the lowest microsporophylls (e.g., Figs. 53–55, 62, 63, and 85). These features are typical for living Agathis when present, although some species can have sessile pollen cones (A. montana, and sometimes A. dammara, A. macrophylla, A. microstachya, and A. silbae) or can produce a single, extended, leaflike lower bract pair (A. australis and A. kinabaluensis). In Araucaria, the pollen cones are usually sessile or have a very short, never elongate peduncle, and the basal bracts, like the foliage leaves, are more numerous and much [Vol. 101 more narrow and sharp-pointed, extending well above the lowest microsporophylls (Cookson and Duigan, 1951; de Laubenfels, 1972, 1988; Barrett, 1998; Hill, 1998; Farjon, 2010). Araucaria pollen-cone size can also be much greater (≤25 cm in length) than in Agathis (≤9 cm), and the fossils (≤5.6 cm). Wollemia pollen cones are sessile and also range above Agathis in size (≤12.5 cm in length); the basal bracts are small, triangular to semirounded, and sharp-pointed and extend onto the basal microsporophylls (Hill, 1998; Eckenwalder, 2009; Farjon, 2010). Wollemia pollen cones are also shed without the bracts, which therefore would not be seen in isolated fossil cones as described here, and they easily disaggregate on drying (as also observed in Araucaria bidwillii), such that the microsporophylls break and leave the cone axis covered in their stubs (Chambers et al., 1998). This situation is unlike that reported for Agathis robusta (Chambers et al., 1998), whose microsporophylls remained intact when separated from the axis of the dried cone axis and left behind “footprint” depressions that appear to be similar to those in some of the fossils (Fig. 66). However, other fossils show broken remnants of the stalk bases rather than pits (Fig. 67). Likewise, when we tried this experiment, also on dried pollen cones of A. robusta (Fig. 79), mostly pits but some base remnants resulted, corresponding to intact (Fig. 81) and “footless” detached microsporophylls, respectively. Peltate microsporophylls, as seen in the fossils (Figs. 57 and 68–72), are typical for Araucariaceae (Gilmore and Hill, 1997). Agathis microsporophylls (in species where these are imbricate; Fig. 81), like those of the fossils, have rounded apices and a thick, long stalk. Unlike the fossils, Araucaria microsporophylls tend to have more pointed, acute apices and a relatively thin, weak, stalk, and Wollemia microsporophylls have very short stalks and thickened, shield-shaped heads with large, angular surface projections (Cookson and Duigan, 1951; Jones et al., 1995; Hill, 1998; Eckenwalder, 2009; Farjon, 2010). Epifluorescent imaging of an A. robusta pollen cone, with microsporophylls in lateral view (Fig. 80), very clearly distinguishes the tissues of the stalk and its expanding median ridge, the apically and deeply basally recurved head, and the abaxial pollen sacs under the basal portion of the recurved head. The same distinctions can be seen in the fossils (Figs. 69–72). Consistent with the observations above, a separate araucariaceous pollen cone morphotype from Laguna del Hunco (exemplar specimen LH13–1135 mentioned by Wilf et al., 2005), under separate study, is larger than the fossils described here and has a very short peduncle, numerous narrow, long, sharppointed, mucronate basal bracts that extend onto the basal microsporophylls, and large, triangular microsporophyll heads with acute to acuminate apices. This morphotype is the probable pollen cone of the Araucaria pichileufensis plant. Comparisons to extant species— Agathis zamunerae is the first fossil Agathis to be so completely preserved as to allow detailed comparisons to living species, using most of the typical botanical characters (Table 1). The following combined character states of Agathis zamunerae, and those of the pollen cones alone, are unlike any other Agathis species (also see Specific diagnosis): leaves with consistently elliptic to lanceolate shape, long length, and generally high length:width ratio; unique combination of seed and wing dimensions; and pollen cones with cylindrical or slightly convex shape, long length, and stout, long, peduncle, relatively few (3) basal bract pairs forming a tightly imbricate cluster with width less than that of the cone body and no elongate basal bracts, and imbricate microsporophylls January 2014] WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA with head width ≤2 mm and entire head margins. Without a phylogenetic context for the genus, it is problematic to evaluate the importance and polarity of the various characters. However, overall, and especially when considering pollen cone characters, Agathis lenticula (Figs. 82–88) emerges as the living species with the greatest morphological similarity to the fossils, though with several differences (Table 1). This species has not been considered in the limited phylogenetic analyses done so far for Agathis, and correcting this omission would have obvious importance for evaluating the phylogenetic position of A. zamunerae, as well as for the conservation of A. lenticula. In A. lenticula, the pollen cones (Fig. 85) are somewhat shorter than the longest fossil cones but otherwise broadly consistent in cylindrical shape (of mature cones), length and stoutness of the peduncle, number and imbrication of bracts, and microsporophyll height, width, and imbrication. However, A. lenticula microsporophylls are noticeably denticulate at the apex, versus entire in the fossils. This difference could be preservational, but the denticulations we have observed in the living species are large enough to be easily seen with a 10× hand lens, and similar structures should be visible in our best-preserved fossils (e.g., Figs. 65 and 71). The seed-cone scales of A. lenticula are consistent with the fossils in size and general shape. The namesake lens-shaped juvenile leaves of A. lenticula (Figs. 83 and 84) were not seen in the fossils. Agathis moorei shows some morphological overlap with the fossils, but its pollen cones have important dissimilarities, and in general its corresponding organs range much larger in size. Pollen cones of A. moorei are consistent with the fossils in cylindrical shape, peduncle length (although this can be significantly longer than in the fossils), imbrication of bracts and microsporophylls, and height and width of microsporophyll heads, although the width can be much greater. However, compared with the fossils, A. moorei pollen cones arise from more slender peduncles, do not become so long, have 4–8 pairs of bracts (vs. three pairs in the fossils), and have relatively flattened microsporophyll heads with denticulate distal margins, compared to convex heads with entire margins in the fossils. The seed-cone scales are also similar to the fossils, but again they tend to be larger, especially in length. Leaf shape is more variable than in the fossils, and leaf size can be similar or much larger. Agathis macrophylla pollen cones are comparable with the fossils in cylindrical shape, peduncle stoutness and length, the imbrication of basal bracts, and the imbrication, height, and width of microsporophylls. However, in A. macrophylla, the attachment of the microsporophyll stalk is not peltate but to the abaxial edge of the head, and the microsporophyll apex is denticulate and can be notched. According to Farjon (2010; Table 1), there are four bract pairs, and the cone does not become so long as in the fossils, whereas Eckenwalder (2009) reported 3–4 bract pairs and cone length that rarely reaches that of the fossils. Seed-cone scales of A. macrophylla are generally larger than in the fossils. Leaf shape is not usually elliptic in A. macrophylla and, consistent with the name, leaf length and width can be significantly larger than in A. zamunerae. Agathis robusta has pollen cones with several dissimilarities from those of A. zamunerae, despite the similar long-cylindrical aspect in both species, most notably: in A. robusta the peduncle can be much longer, there are usually more bract pairs and these are often distinctly less imbricate, and the microsporophylls are often tessellate or only weakly imbricate. Also, cone scales of A. robusta are usually larger than in the fossils. These living and fossil species are most similar to each other in leaf size and shape. 175 Agathis australis of New Zealand, of general interest because it emerges as the sister of all the remaining species in most molecular phylogenies, and because its history in New Zealand is frequently debated (see General remarks), has many important morphological differences from A. zamunerae. Many of these are smaller dimensions of the organs (Table 1), but additional differences from the fossils are that A. australis has: pollencone peduncles that can be much longer; pollen-cone bract clusters loosely arranged and extending past the width of the cone, often with subtending, leaflike, long bracts; microsporophyll heads wider; seed-cone scales with very distinct narrow, triangular, mucronate apical projections; (adult) leaves often with a truncate apex and longitudinally oriented stomata; and seed-wings with a square shape. These numerous differences from A. australis support the idea that A. zamunerae occupies a derived position within the genus. Agathis dammara resembles and is often considered conspecific with A. lenticula (Whitmore, 1980b; Eckenwalder, 2009). In A. dammara, the basal bracts of pollen cones can be more numerous (2–4 pairs) than in A. lenticula (2–3) and the fossils (3) and are spreading rather than imbricate. Other differences from the fossils are mostly dimensional (e.g., A. dammara has shorter pollen cones and peduncles, and larger seed-cone scales). The microsporophylls of A. dammara, A. lenticula, and A. zamunerae are very similar, except that microsporophyll height in A. dammara is distinctly lower than in the other two species, and in both the living species the apical margins are denticulate, versus entire in the fossils. Finally, A. borneensis is another species with some general similarities to the fossils, mostly in the leaves, but its pollen cones are very different. They are not strongly cylindrical and can be globose when immature, but most notably, the pollen cones and microsporophylls become dramatically larger than those of the fossils or of any other living Agathis species. Remarks on Agathis lenticula— Agathis lenticula (Figs. 82–88) may possess special evolutionary and biogeographic importance for the genus, given its similarity to the fossil species A. zamunerae. Agathis lenticula is a large tree (≤45 m) that is endemic to the lower montane forests of northern Borneo (Malaysia; de Laubenfels, 1979; Yii, 1995). The Kinabalu Park Headquarters Meteorological Station (1680 m), around which A. lenticula is abundant, has a mean monthly temperature of ca. 20°C, with an annual range of 14.4–22.2°C, and annual precipitation of 2000–3800 mm, including drought years (Kitayama, 1992). Where it is still protected, we found the species to be common and often dominant, for example along the lower reaches of the Mesilau trail, in the eastern portion of Kinabalu National Park (P. Wilf and R. M. Kooyman, personal observation). This species is considered Vulnerable and suffers ongoing losses within its limited range (Fig. 88) that are not well documented because loggers do not discriminate it from A. borneensis (Beaman and Beaman, 1993; Farjon et al., 1993; Farjon, 2010; IUCN, 2013). We note that Whitmore (1980b) and Eckenwalder (2009) did not recognize A. lenticula as distinct from the more widespread A. dammara, which if incorrect would be very likely to have negative conservation effects on A. lenticula. In our experience, the characters of A. lenticula are reliably distinct from A. dammara as originally proposed (de Laubenfels, 1979; Farjon, 2010), and we recommend that the species be managed in that context. 176 [Vol. 101 AMERICAN JOURNAL OF BOTANY It is remarkable that Mt. Kinabalu alone has three species of Agathis (A. borneensis, A. lenticula, and A. kinabaluensis ) and that these form part of a diverse and entirely Gondwanan conifer assemblage that also has six genera and 16 species of Podocarpaceae, along with their close relative Phyllocladus hypophyllus (Beaman and Beaman, 1993, 1998). Including A. orbicula, Borneo as a whole has four species of Agathis, equal to New Caledonia (Table 1). Also striking is that one of the tall podocarps that frequently cooccurs with Agathis lenticula, Dacrycarpus imbricatus, is extremely similar to D. puertae from Laguna del Hunco and Río Pichileufú (Wilf, 2012) at ca. 16 000 km modern distance, further illustrating the vast temporal and geographic reach of a Gondwanan association surviving in an Asian rainforest. General comments— The evidence from Agathis zamunerae, including the strong possibility that it represents a derived lineage, suggests that modern-aspect Agathis not only occupied a vast land area by the early Eocene but was already well diversified. As for Eucalyptus and many other taxa (see Materials and Methods), Eocene Agathis fossils from Patagonia show that Australia can no longer be assumed to be the area of origin for the genus. Agathis evolved in and became a dominant element of the extensive southern rainforest biome of the Eocene, and in all likelihood it once inhabited Antarctica, which had very warm temperatures at this time (Pross et al., 2012), along with Australia and South America. Agathis was probably restricted primarily to rainforest environments throughout its history, partly because it possesses accessory xylem tissues parallel to the leaf veins (Kausik, 1976) that are likely to collapse during drought (Brodribb and Holbrook, 2005; these run adjacent to the veins and could not be distinguished in the compression fossils). There is a vigorous debate concerning the origins of Agathis in New Zealand and, along with many other components of the New Zealand biota, regarding its possible survival there through a proposed interval of partial or complete submergence during the Oligocene (Cooper and Millener, 1993; Stöckler et al., 2002; Waters and Craw, 2006; Knapp et al., 2007; Lee et al., 2007; Biffin et al., 2010; Crisp and Cook, 2011; Sharma and Wheeler, 2013). Our results show, first, that modern-aspect Agathis was present long before the Oligocene, over a vast area of Gondwana before its final breakup. Thus, putative survival in situ was possible in that the genus had certainly evolved by that time, but whether Agathis was really in New Zealand during the Oligocene is not fully understood despite many possible fossils (Pole, 2008). Second, the large past distribution of Agathis revealed here shows that many areas of Gondwana, not just Australia (as thought based on the previous fossil record), could have been the source for New Zealand in a dispersal scenario. This situation is similar to that of New Zealand’s endemic tuatara lizard (Sphenodon), for which there is a global record of related fossil forms during the Jurassic, and now an especially tuatara-like fossil is known from the Campanian–Maastrichtian of Patagonia (Apesteguía and Jones, 2012). Third, A. zamunerae is the only fossil Agathis that can be well compared to living species because of its preservation of a large suite of characters from multiple organs, and in all probability it is not closely related to A. australis (see Comparisons to extant species). Therefore, there is still no reliable fossil evidence, from New Zealand or elsewhere, concerning the origins of the A. australis lineage. Agathis zamunerae is the oldest example of a modern-aspect Agathis, but at the same time it is significantly younger than the oldest Araucaria (Middle Jurassic), in line with the abundant molecular data that show Araucaria to be sister to Agathis plus Wollemia, and the relatively late (Turonian) appearance of Wollemia-type pollen (Dilwynites; Macphail et al., 1995; Macphail and Carpenter, 2013). Early Paleocene vegetative and fertile macrofossils from the San Jorge Basin in Chubut of a probable stem taxon of Agathis, currently under study, corroborate the idea of a Paleogene crown for Agathis and show an even older ex-Australasian distribution for the Agathis lineage (I. H. Escapa et al., unpublished data). Conclusions— Agathis zamunerae sp. nov. shows a large suite of character states that are all found in living Agathis and demonstrates that the lineage was present by the early Eocene, in turn helping to validate the Australian early Cenozoic record of the genus. The presence of Agathis in both Australia and Patagonia just prior to and during the middle Eocene terminal breakup of Gondwana clearly indicates that its range during the globally warm Eocene was vast and must have included Antarctica, as is true of other fossil taxa that were previously shown to have had similar past distributions and that are also frequently associated with Agathis today. The new species was a dominant component of the ancient Patagonian rainforest biome, as indicated by its relatively high leaf abundance. Assuming that A. zamunerae of Patagonia was similar to living Agathis in having large stature, long life span, and keystone ecological roles, its extinction was an important contributor to the ecosystem transformation process in Patagonia from the ancient, high-diversity rainforests, eventually leading to its modern-day, carbon-poor steppe and species-poor temperate rainforest biomes. This natural process took many millions of years, but in its present range, many thousands of kilometers distant from Patagonia, the rapid loss of Agathis forest is having comparable impacts, several orders of magnitude more rapidly. As in the past, the present loss of Agathis is correlated with massive ecosystem disturbances and may well portend a threshold event, whereas success in conserving the genus seems likely to be correlated with many aspects of improved ecosystem health and biodiversity. LITERATURE CITED APESTEGUÍA, S., AND M. E. H. JONES. 2012. A Late Cretaceous “tuatara” (Lepidosauria: Sphenodontinae) from South America. Cretaceous Research 34: 154–160. ARAGÓN, E., AND M. M. MAZZONI. 1997. Geología y estratigrafía del complejo volcánico piroclástico del Río Chubut medio (Eoceno), Chubut, Argentina. Revista de la Asociación Geológica Argentina 52: 243–256. ARAGÓN, E., AND E. J. ROMERO. 1984. Geología, paleoambientes y paleobotánica de yacimientos Terciarios del occidente de Río Negro, Neuquén y Chubut. Actas del IX Congreso Geológico Argentino, San Carlos de Bariloche 4: 475–507. AXSMITH, B. J., T. N. TAYLOR, AND E. L. TAYLOR. 1998. Anatomically preserved leaves of the conifer Notophytum krauselii (Podocarpaceae) from the Triassic of Antarctica. American Journal of Botany 85: 704–713. BALETE, D. S., L. R. HEANEY, M. JOSEFA VELUZ, AND E. A. RICKART. 2009. Diversity patterns of small mammals in the Zambales Mts., Luzon, Philippines. Mammalian Biology 74: 456–466. BARRETT, W. H. 1998. Gymnospermae. In M. N. Correa [ed.], Flora Patagonica, parte I, 370–384. Instituto Nacional de Tecnología Agropecuaria, Buenos Aires, Argentina. January 2014] WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA BEAMAN, J. H., AND R. S. BEAMAN. 1993. The gymnosperms of Mount Kinabalu. Contributions from the University of Michigan Herbarium 19: 307–340. BEAMAN, J. H., AND R. S. BEAMAN. 1998. The plants of Mount Kinabalu 3. Gymnosperms and non-orchid monocotyledons. Natural History Publications (Borneo), Kota Kinabalu, Malaysia. BERRY, E. W. 1922. The flora of the Concepción-Arauco coal measures of Chile. Johns Hopkins University Studies in Geology 4: 73–143. BERRY, E. W. 1925. A Miocene flora from Patagonia. Johns Hopkins University Studies in Geology 6: 183–251. BERRY, E. W. 1935a. A fossil Cochlospermum from northern Patagonia. Bulletin of the Torrey Botanical Club 62: 65–67. BERRY, E. W. 1935b. A Tertiary Ginkgo from Patagonia. Torreya 35: 11–13. BERRY, E. W. 1935c. The Monimiaceae and a new Laurelia. Botanical Gazette (Chicago, Ill.) 96: 751–754. BERRY, E. W. 1938. Tertiary flora from the Río Pichileufú, Argentina. Geological Society of America. Special Paper 12: 1–149. BIFFIN, E., R. S. HILL, AND A. J. LOWE. 2010. Did Kauri (Agathis: Araucariaceae) really survive the Oligocene drowning of New Zealand? Systematic Biology 59: 594–602. BIGWOOD, A. J., AND R. S. HILL. 1985. Tertiary araucarian macrofossils from Tasmania. Australian Journal of Botany 33: 645–656. BISHOP, K. D. 1992. The Standardwing Bird of Paradise Semioptera wallacii (Paradisaeidae), its ecology, behaviour, status and conservation. Emu 92: 72–78. BOWEN, M. R., AND T. C. WHITMORE. 1980a. A second look at Agathis. CFI Occasional Papers 13: 1–19. BOWEN, M. R., AND T. C. WHITMORE. 1980b. Agathis—A genus of fast growing rain forest conifers. Commonwealth Forestry Review 59: 307–310. BRODRIBB, T. J., AND R. S. HILL. 1999. Southern conifers in time and space. Australian Journal of Botany 47: 639–696. BRODRIBB, N. M. HOLBROOK. 2005. Water stress deforms tracheids peripheral to the leaf vein of a tropical conifer. Plant Physiology 137: 1139–1146. BURNHAM, R. J., S. L. WING, AND G. G. PARKER. 1992. The reflection of deciduous forest communities in leaf litter: Implications for autochthonous litter assemblages from the fossil record. Paleobiology 18: 30–49. BURROWS, G. E., AND S. BULLOCK. 1999. Leaf anatomy of Wollemi pine (Wollemia nobilis, Araucariaceae). Australian Journal of Botany 47: 795–806. CARPENTER, R. J., R. S. HILL, AND G. J. JORDAN. 1994. Cenozoic vegetation in Tasmania: Macrofossil evidence. In R. S. Hill [ed.], History of the Australian vegetation: Cretaceous to Recent, 276–298. Cambridge University Press, Cambridge, UK. CARVALHO, M. R., P. WILF, E. J. HERMSEN, M. A. GANDOLFO, N. R. CÚNEO, AND K. R. JOHNSON. 2013. First record of Todea (Osmundaceae) in South America, from the early Eocene paleorainforests of Laguna del Hunco (Patagonia, Argentina). American Journal of Botany 100: 1831–1848. CHAMBERS, T. C., A. N. DRINNAN, AND S. MCLOUGHLIN. 1998. Some morphological features of Wollemi pine (Wollemia nobilis: Araucariaceae) and their comparison to Cretaceous plant fossils. International Journal of Plant Sciences 159: 160–171. CONRAN, J. G., G. M. WOOD, P. G. MARTIN, J. M. DOWD, C. J. QUINN, P. A. GADEK, AND R. A. PRICE. 2000. Generic relationships within and between the gymnosperm families Podocarpaceae and Phyllocladaceae based on an analysis of the chloroplast gene rbcL. Australian Journal of Botany 48: 715–724. COOKSON, I. C., AND S. L. DUIGAN. 1951. Tertiary Araucariaceae from south-eastern Australia, with notes on living species. Australian Journal of Scientific Research Ser.B 4: 415–449. COOPER, R. A., AND P. R. MILLENER. 1993. The New Zealand biota: Historical background and new research. Trends in Ecology & Evolution 8: 429–433. CRISP, M. D., AND L. G. COOK. 2011. Cenozoic extinctions account for the low diversity of extant gymnosperms compared with angiosperms. The New Phytologist 192: 997–1009. DE LAUBENFELS, D. J. 1972. 177 Gymnosperms. Flore de la Nouvelle Calédonie et dépendances, vol. 4. Muséum National D’Histoire Naturelle, Paris, France. DE LAUBENFELS, D. J. 1979. The species of Agathis (Araucariaceae) of Borneo. Blumea 25: 531–541. DE LAUBENFELS, D. J. 1988. Coniferales. Flora Malesiana series I 10: 337–453. DETTMANN, M. E., H. T. CLIFFORD, AND M. PETERS. 2012. Emwadea microcarpa gen. et sp. nov.—Anatomically preserved araucarian seed cones from the Winton Formation (late Albian), western Queensland, Australia. Alcheringa 36: 217–237. DIMICHELE, W. A., S. H. MAMAY, D. S. CHANEY, R. W. HOOK, AND J. W. NELSON. 2001. An Early Permian flora with Late Permian and Mesozoic affinities from north-central Texas. Journal of Paleontology 75: 449–460. DUMBLETON, L. J. 1952. A new genus of seed-infesting micropterygid moths. Pacific Science 6: 17–29. ECKENWALDER, J. E. 2009. Conifers of the world: The complete reference. Timber Press, Portland, Oregon, USA. ECROYD, C. E. 1982. Biological flora of New Zealand 8. Agathis australis (D. Don) Lindl. (Araucariaceae) Kauri. New Zealand Journal of Botany 20: 17–36. ENGELHARDT, H. 1891. Ueber Tertiärpflanzen von Chile. Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft 16: 629–692. ENRIGHT, N. J. 1995. Conifers of tropical Australasia. In N. J. Enright and R. S. Hill [eds.], Ecology of the southern conifers, 223–251. Smithsonian Institution Press, Washington, D.C., USA. ENRIGHT, N. J., AND J. OGDEN. 1987. Decomposition of litter from common woody species of kauri (Agathis australis Salisb.) forest in northern New Zealand. Australian Journal of Ecology 12: 109–124. ESCAPA, I. H., AND S. A. CATALANO. 2013. Phylogenetic analysis of Araucariaceae: Integrating molecules, morphology, and fossils. International Journal of Plant Sciences 174: 1153–1170. FARJON, A. 2010. A handbook of the world’s conifers. Brill, Leiden, The Netherlands. FARJON, A., C. N. PAGE, AND N. SCHELLEVIS. 1993. A preliminary world list of threatened conifer taxa. Biodiversity and Conservation 2: 304–326. FLORIN, R. 1931. Untersuchungen zur Stammesgeschichte der Coniferales und Cordaitales. Kungliga Svenska Vetenskapsakademiens Handlingar 10: 1–588. FLORIN, R. 1940a. The Tertiary conifers of south Chile and their phytogeographical significance. Kungliga Svenska Vetenskapsakademiens Handlingar 19: 1–107. FLORIN, R. 1940b. Die heutige und frühere Verbreitung der Koniferengattung Acmopyle Pilger. Svensk Botanisk Tidskrift 34: 117–140. FLORIN, R. 1963. The distribution of conifer and taxad genera in time and space. Acta Horti Bergiani 20: 121–312. GANDOLFO, M. A., M. C. DIBBERN, AND E. J. ROMERO. 1988. Akania patagonica n. sp. and additional material on Akania americana Romero & Hickey (Akaniaceae), from Paleocene sediments of Patagonia. Bulletin of the Torrey Botanical Club 115: 83–88. GANDOLFO, M. A., AND E. J. HERMSEN. 2012. The emerging Patagonian fossil record of Cunoniaceae and its biogeographical significance. Japanese Journal of Palynology 58 (Special Issue, Abstracts: IPC/ IOPC 2012): 66–67. GANDOLFO, M. A., E. J. HERMSEN, M. C. ZAMALOA, K. C. NIXON, C. C. GONZÁLEZ, P. WILF, N. R. CÚNEO, AND K. R. JOHNSON. 2011. Oldest known Eucalyptus macrofossils are from South America. PLoS ONE 6: e21084. GILMORE, S., AND K. D. HILL. 1997. Relationships of the Wollemi pine (Wollemia nobilis) and a molecular phylogeny of the Araucariaceae. Telopea 7: 275–291. GONZÁLEZ, C. C., M. A. GANDOLFO, M. C. ZAMALOA, N. R. CÚNEO, P. WILF, AND K. R. JOHNSON. 2007. Revision of the Proteaceae macrofossil record from Patagonia, Argentina. Botanical Review 73: 235–266. GORMAN, M. L. 1975. Habitats of the land-birds of Viti Levu, Fiji islands. Ibis 117: 152–161. 178 AMERICAN JOURNAL OF BOTANY GREENE, T. C. 1998. Foraging ecology of the red-crowned parakeet (Cyanoramphus novaezelandiae novaezelandiae) and yellow-crowned parakeet (C. auriceps auriceps) on Little Barrier Island, Hauraki Gulf, New Zealand. New Zealand Journal of Ecology 22: 161–171. HENKEL, J. B., AND W. HOCHSTETTER. 1865. Synopsis der Nadelhölzer. Verlag der J. G. Cottaschen Buchhandlung, Stuttgart, Germany. HERMSEN, E. J., M. A. GANDOLFO, AND M. C. ZAMALOA. 2012. The fossil record of Eucalyptus in Patagonia. American Journal of Botany 99: 1356–1374. HICKEY, L. J., AND R. K. PETERSON. 1978. Zingiberopsis, a fossil genus of the ginger family from Late Cretaceous to early Eocene sediments of Western Interior North America. Canadian Journal of Botany 56: 1136–1152. HILL, K. D. 1998. Pinophyta. Flora of Australia 48: 545–596. HILL, R. S. 1994. The history of selected Australian taxa. In R. S. Hill [ed.], History of the Australian vegetation: Cretaceous to Recent, 390–419. Cambridge University Press, Cambridge, UK. HILL, R. S. 1995. Conifer origin, evolution, and diversification in the Southern Hemisphere. In N. J. Enright and R. S. Hill [eds.], Ecology of the southern conifers, 10–29. Smithsonian Institution Press, Washington, D.C., USA. HILL, R. S., AND A. J. BIGWOOD. 1987. Tertiary gymnosperms from Tasmania: Araucariaceae. Alcheringa 11: 325–335. HILL, R. S., AND M. S. POLE. 1992. Leaf and shoot morphology of extant Afrocarpus, Nageia and Retrophyllum (Podocarpaceae) species, and species with similar leaf arrangement, from Tertiary sediments in Australasia. Australian Systematic Botany 5: 337–358. HILL, R. S., AND L. J. SCRIVEN. 1998. The fossil record of conifers in Australia. Flora of Australia 48: 527–537. HILL, R. S., T. LEWIS, R. J. CARPENTER, AND S. S. WHANG. 2008. Agathis (Araucariaceae) macrofossils from Cainozoic sediments in southeastern Australia. Australian Systematic Botany 21: 162–177. HOLLICK, A. 1932. Descriptions of new species of Tertiary cycads, with a review of those previously recorded. Bulletin of the Torrey Botanical Club 59: 169–189. HOWCROFT, N. H. S. 1987. Phenology and silviculture of New Guinea kauri pine (Agathis sp). Klinkii 3: 53–64. HYLAND, B. P. M. 1977. A revision of the genus Agathis (Araucariaceae) in Australia. Brunonia 1: 103–115. IGLESIAS, A. 2013. Alba B. Zamuner (1959–2012). Ameghiniana 49: 675. IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www. iucnredlist.org>. Downloaded on 04 January 2014. JAFFRÉ, T., J. MUNZINGER, AND P. P. LOWRY II. 2010. Threats to the conifer species found on New Caledonia’s ultramafic massifs and proposals for urgently needed measures to improve their protection. Biodiversity and Conservation 19: 1485–1502. JONES, W. G., K. D. HILL, AND J. M. ALLEN. 1995. Wollemia nobilis, a new living Australian genus and species in the Araucariaceae. Telopea 6: 173–176. JONGKIND, A., E. VELTHORST, AND P. BUURMAN. 2007. Soil chemical properties under kauri (Agathis australis) in the Waitakere Ranges, New Zealand. Geoderma 141: 320–331. JORDAN, G. J., R. J. CARPENTER, J. M. BANNISTER, D. E. LEE, D. C. MILDENHALL, AND R. S. HILL. 2011. High conifer diversity in OligoMiocene New Zealand. Australian Systematic Botany 24: 121–136. KAUR, D., AND S. P. BHATNAGAR. 1986. Studies in the family Araucariaceae: Female cone development in Agathis robusta. Phytomorphology 36: 129–143. KAUSIK, S. B. 1976. A contribution to foliar anatomy of Agathis dammara, with a discussion on the transfusion tissue and stomatal structure. Phytomorphology 26: 263–273. KIRK, T. 1889. The forest flora of New Zealand. George Didsbury, Government Printer, Wellington, New Zealand. KITAYAMA, K. 1992. An altitudinal transect study of the vegetation on Mount Kinabalu, Borneo. Vegetatio 102: 149–171. KITAMURA, K., AND M. Y. ABDUL RAHMAN. 1992. Genetic diversity among natural populations of Agathis borneensis (Araucariaceae), a tropical rain forest conifer from Brunei Darussalam, Borneo, Southeast Asia. Canadian Journal of Botany 70: 1945–1949. [Vol. 101 KNAPP, M., R. MUDALIAR, D. HAVELL, S. J. WAGSTAFF, AND P. J. LOCKHART. 2007. The drowning of New Zealand and the problem of Agathis. Systematic Biology 56: 862–870. KNIGHT, C. L., AND P. WILF. 2013. Rare leaf fossils of Monimiaceae and Atherospermataceae (Laurales) from Eocene Patagonian rainforests and their biogeographic significance. Palaeontologia Electronica 16: article 16.3.27A. KUNZMANN, L. 2007. Araucariaceae (Pinopsida): Aspects in palaeobiogeography and palaeobiodiversity in the Mesozoic. Zoologischer Anzeiger 246: 257–277. LEE, D. E., J. M. BANNISTER, AND J. K. LINDQVIST. 2007. Late Oligocene– Early Miocene leaf macrofossils confirm a long history of Agathis in New Zealand. New Zealand Journal of Botany 45: 565–578. LESLIE, A. B., J. M. BEAULIEU, H. S. RAI, P. R. CRANE, M. J. DONOGHUE, AND S. MATHEWS. 2012. Hemisphere-scale differences in conifer evolutionary dynamics. Proceedings of the National Academy of Sciences, USA 109: 16217–16221. LIU, N., Y. ZHU, Z. WEI, J. CHEN, Q. WANG, S. JIAN, D. ZHOU, J. SHI, Y. YANG, AND Y. ZHONG. 2009. Phylogenetic relationships and divergence times of the family Araucariaceae based on the DNA sequences of eight genes. Chinese Science Bulletin 54: 2648–2655. MABBERLEY, D. J. 2002. The coming of the kauris. Curtis’s Botanical Magazine 19: 252–264. MACPHAIL, M., AND R. J. CARPENTER. 2013. New potential nearest living relatives for Araucariaceae producing fossil Wollemi Pine-type pollen (Dilwynites granulatus W.K. Harris, 1965). Alcheringa 38: DOI:10. 1080/03115518.2014.843145. MACPHAIL, M., R. J. CARPENTER, A. IGLESIAS, AND P. WILF. 2013. First evidence for Wollemi Pine-type pollen (Dilwynites: Araucariaceae) in South America. PLoS ONE 8: e69281. MACPHAIL, M., K. HILL, A. D. PARTRIDGE, AND E. M. TRUSWELL. 1995. ‘Wollemi Pine’—Old pollen records for a newly discovered genus of gymnosperm. Geology Today 11: 48–50. MEIJER DREES, E. 1940. The genus Agathis in Malaysia. Bulletin du Jardin Botanique de Buitenzorg Sér.3 16: 455–474. MILLER, I. M., AND L. J. HICKEY. 2010. The fossil flora of the Winthrop Formation (Albian-Early Cretaceous) of Washington State, USA. Part II: Pinophytina. Bulletin of the Peabody Museum of Natural History 51: 3–96. MIRAMS, R. V. 1957. Aspects of the natural regeneration of the kauri (Agathis australis Salisb.). Transactions of the Royal Society of New Zealand 84: 661–680. MOORE, S., C. D. EVANS, S. E. PAGE, M. H. GARNETT, T. G. JONES, C. FREEMAN, A. HOOIJER, A. J. WILTSHIRE, S. H. LIMIN, AND V. GAUCI. 2013. Deep instability of deforested tropical peatlands revealed by fluvial organic carbon fluxes. Nature 493: 660–663. MORROGH-BERNARD, H., S. HUSSON, S. E. PAGE, AND J. O. RIELEY. 2003. Population status of the Bornean orang-utan (Pongo pygmaeus) in the Sebangau peat swamp forest, Central Kalimantan, Indonesia. Biological Conservation 110: 141–152. OFFLER, C. E. 1984. Extant and fossil Coniferales of Australia and New Guinea, Part 1: A study of the external morphology of the vegetative shoots of the extant species. Palaeontographica Abt.B 193: 18–120. OWENS, J. N., G. L. CATALANO, AND J. AITKEN-CHRISTIE. 1997. The reproductive biology of kauri (Agathis australis). IV. Late embryogeny, histochemistry, cone and seed morphology. International Journal of Plant Sciences 158: 395–407. PANTI, C., R. R. PUJANA, M. C. ZAMALOA, AND E. J. ROMERO. 2012. Araucariaceae macrofossil record from South America and Antarctica. Alcheringa 36: 1–22. PETERSEN, C. S. 1946. Estudios geológicos en la región del Río Chubut medio. Dirección de Minas y Geología Boletín 59: 1–137. POLE, M. 2008. The record of Araucariaceae macrofossils in New Zealand. Alcheringa 32: 405–426. PROSS, J., L. CONTRERAS, P. K. BIJL, D. R. GREENWOOD, S. M. BOHATY, S. SCHOUTEN, J. A. BENDLE, ET AL. 2012. Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch. Nature 488: 73–77. January 2014] WILF ET AL.—EOCENE AGATHIS FROM SOUTH AMERICA QUINN, C. J., R. A. PRICE, AND P. A. GADEK. 2002. Familial concepts and relationships in the conifers based on rbcL and matK sequence comparisons. Kew Bulletin 57: 513–531. RAI, H. S., P. A. REEVES, R. PEAKALL, R. G. OLMSTEAD, AND S. W. GRAHAM. 2008. Inference of higher-order conifer relationships from a multilocus plastid data set. Botany 86: 658–669. RIPLEY, S. D. 1964. A systematic and ecological study of birds of New Guinea. Bulletin of the Peabody Museum of Natural History 19: 1–87. ROMERO, E. J., AND L. J. HICKEY. 1976. A fossil leaf of Akaniaceae from Paleocene beds in Argentina. Bulletin of the Torrey Botanical Club 103: 126–131. SALISBURY, R. A. 1807. The characters of several genera in the natural order of Coniferae: With remarks on their stigmata, and cotyledons. Transactions of the Linnean Society of London 8: 308–317. SETOGUCHI, H., T. A. OSAWA, J.-C. PINTAUD, T. JAFFRÉ, AND J.-M. VEILLON. 1998. Phylogenetic relationships within Araucariaceae based on rbcL gene sequences. American Journal of Botany 85: 1507–1516. SEWARD, A. C., AND S. O. FORD. 1906. The Araucariaceae, recent and extinct. Proceedings of the Royal Society of London, Series B 77: 163–164. SHARMA, P. P., AND W. C. WHEELER. 2013. Revenant clades in historical biogeography: The geology of New Zealand predisposes endemic clades to root age shifts. Journal of Biogeography 40: 1609–1618. SILVESTER, W. B., AND T. A. ORCHARD. 1999. The biology of kauri (Agathis australis) in New Zealand. I. Production, biomass, carbon storage, and litter fall in four forest remnants. New Zealand Journal of Botany 37: 553–571. SOERIANEGARA, I., N. R. DE GRAAF, J. M. FUNDTER, J. W. HILDEBRAND, A. MARTAWIJAYA, J. ILIC, AND C. C. H. JONGKIND. 1993. Agathis. In I. Soerianegara and R. H. M. J. Lemmens [eds.], Plant resources of South-East Asia 5 (1). Timber trees: Major commercial timbers, 73–82. Pudoc Scientific Publishers, Wageningen, The Netherlands. STEFANOVIĆ, S., M. JAGER, J. DEUTSCH, J. BROUTIN, AND M. MASSELOT. 1998. Phylogenetic relationships of conifers inferred from partial 28S rRNA gene sequences. American Journal of Botany 85: 688–697. STERLING, C. 1958. Dormant apical bud of Agathis lanceolata. Botanical Gazette (Chicago, Ill.) 120: 49–53. STOCKEY, R. A. 1982. The Araucariaceae: An evolutionary perspective. Review of Palaeobotany and Palynology 37: 133–154. STOCKEY, R. A., AND I. J. ATKINSON. 1993. Cuticle micromorphology of Agathis Salisbury. International Journal of Plant Sciences 154: 187–225. STOCKEY, R. A., AND T. N. TAYLOR. 1981. Scanning electron microscopy of epidermal patterns and cuticular structure in the genus Agathis. Scanning Electron Microscopy 3: 207–212. STÖCKLER, K., I. L. DANIEL, AND P. J. LOCKHART. 2002. New Zealand kauri (Agathis australis (D. Don) Lindl., Araucariaceae) survives Oligocene drowning. Systematic Biology 51: 827–832. 179 TOWNS, D. R. 1981. Life histories of benthic invertebrates in a kauri forest stream in northern New Zealand. Australian Journal of Marine and Freshwater Research 32: 191–211. VERKAIK, E., AND W. G. BRAAKHEKKE. 2007. Kauri trees (Agathis australis) affect nutrient, water and light availability for their seedlings. New Zealand Journal of Ecology 31: 39–46. WATERS, J. M., AND D. CRAW. 2006. Goodbye Gondwana? New Zealand biogeography, geology, and the problem of circularity. Systematic Biology 55: 351–356. WHITMORE, T. C. 1977. A first look at Agathis. Tropical Forestry Papers 11: 1–54. WHITMORE, T. C. 1980a. Utilization, potential, and conservation of Agathis, a genus of tropical Asian conifers. Economic Botany 34: 1–12. WHITMORE, T. C. 1980b. A monograph of Agathis. Plant Systematics and Evolution 135: 41–69. WILCOVE, D. S., X. GIAM, D. P. EDWARDS, B. FISHER, AND L. P. KOH. 2013. Navjot’s nightmare revisited: Logging, agriculture, and biodiversity in Southeast Asia. Trends in Ecology & Evolution 28: 531–540. WILF, P. 2012. Rainforest conifers of Eocene Patagonia: Attached cones and foliage of the extant southeast-Asian and Australasian genus Dacrycarpus (Podocarpaceae). American Journal of Botany 99: 562–584. WILF, P., N. R. CÚNEO, K. R. JOHNSON, J. F. HICKS, S. L. WING, AND J. D. OBRADOVICH. 2003. High plant diversity in Eocene South America: Evidence from Patagonia. Science 300: 122–125. WILF, P., K. R. JOHNSON, N. R. CÚNEO, M. E. SMITH, B. S. SINGER, AND M. A. GANDOLFO. 2005. Eocene plant diversity at Laguna del Hunco and Río Pichileufú, Patagonia, Argentina. American Naturalist 165: 634–650. WILF, P., S. A. LITTLE, A. IGLESIAS, M. C. ZAMALOA, M. A. GANDOLFO, N. R. CÚNEO, AND K. R. JOHNSON. 2009. Papuacedrus (Cupressaceae) in Eocene Patagonia, a new fossil link to Australasian rainforests. American Journal of Botany 96: 2031–2047. WISE, K. A. J. 1962. Parectopa leucocyma (Meyrick) (Lepidoptera: Gracillariidae) rediscovered as a leaf-miner of Kauri (Agathis australis Salisb.). Transactions of the Royal Society of New Zealand. Zoology 1: 373–375. WONG, K. M., AND A. PHILLIPPS, EDS. 1996. Kinabalu, summit of Borneo. Sabah Society, Kota Kinabalu, Malaysia. WYSE, S. V. 2012. Growth responses of five forest plant species to the soils formed beneath New Zealand kauri (Agathis australis). New Zealand Journal of Botany 50: 411–421. YII, P. C. 1995. Araucariaceae. In E. Soepadmo and K. M. Wong [eds.], Tree flora of Sabah and Sarawak. Volume One, 27–32. Forest Research Institute Malaysia, Kuala Lumpur. ZAMALOA, M. C., M. A. GANDOLFO, C. C. GONZÁLEZ, E. J. ROMERO, N. R. CÚNEO, AND P. WILF. 2006. Casuarinaceae from the Eocene of Patagonia, Argentina. International Journal of Plant Sciences 167: 1279–1289.

Int. J. Plant Sci. 182(3):000–000. 2021. q 2021 by The University of Chicago. All rights reserved. 1058-5893/2021/18203-00XX$15.00 DOI: 10.1086/712427 FIRST SOUTH AMERICAN RECORD OF WINTEROXYLON, EOCENE OF LAGUNA DEL HUNCO (CHUBUT, PATAGONIA, ARGENTINA): NEW LINK TO AUSTRALASIA AND MALESIA Mariana Brea,1,*,† Ari Iglesias,‡ Peter Wilf,§ Eliana Moya,* and María A. Gandolfo∥ *Laboratorio de Paleobotánica, Centro de Investigación Cientíﬁca y de Transferencia Tecnológica a la Producción, Consejo Nacional de Investigaciones Cientíﬁcas y Técnicas and Facultad de Ciencia y Tecnología, Provincia de Entre Ríos, Universidad Autónoma de Entre Ríos, España 149, E3105BWA Diamante, Entre Ríos, Argentina; †Cátedra de Paleobotánica, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Calle 122 y 60 s/n, 1900 La Plata, Buenos Aires, Argentina; ‡Instituto de Investigaciones en Biodiversidad y Medioambiente, Consejo Nacional de Investigaciones Cientíﬁcas y Técnicas, Universidad Nacional del Comahue, Quintral 1250, 8400 San Carlos de Bariloche, Río Negro, Argentina; §Department of Geosciences and Earth and Environmental Systems Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA; and ∥L. H. Bailey Hortorium, Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York 14850, USA Editor: Alexandru M.F. Tomescu Premise of research. Winteraceae, a family within the Canellales, is composed of tropical trees and shrubs broadly distributed in the Southern Hemisphere. The family is found today in eastern Australia, New Zealand, Malesia, Oceania, Madagascar, and the Neotropics across a range of dry to wet tropical to temperate climate regions. The fossil record of woods related to the Winteraceae in the Southern Hemisphere is limited to the Late Cretaceous of the Antarctic Peninsula. Here, we present a detailed anatomical description of the secondary xylem of a well-preserved trunk from the early Eocene Laguna del Hunco site, Huitrera Formation, Patagonia (Chubut Province, Argentina), that is referable to a new species of the genus Winteroxylon (Gottwald) Poole and Francis. Methodology. The wood is preserved as a siliceous permineralization; it was sectioned using standard petrographic techniques and observed under both light and scanning electron microscopy. The anatomy was compared with that of extant and fossil species of Winteraceae. Pivotal results. The diagnostic anatomical features of Winteraceae preserved in the fossil include an absence of growth rings, a lack of vessels, tracheids that are rectangular in cross section with circular bordered pits, diffuse axial parenchyma, rays showing two distinct size ranges (uniseriate-biseriate or multiseriate, 3–15 cells wide), and the presence of heterocellular rays containing sclerotic nests, cells with dark contents, and oil cells. The new fossil species most resembles extant genera within the Zygogynum s.l. clade from Australasian and Malesian rain forests; its anatomy is very similar to that of the extant genus Bubbia. The new Patagonian Winteraceae fossil wood is characterized by the presence of sclerotic nests and oil cells in the rays, which differ from those of previously described species of Winteroxylon. Conclusions. On the basis of the distinctive characters preserved, we erect Winteroxylon oleiferum sp. nov. The new fossil is the ﬁrst reliable macrofossil record of Winteraceae from South America, supporting the abundant palynological record of the family from the continent, and it is the oldest record of the Zygogynum s.l. clade, adding to the long list of southern biogeographic connections between South America and Australasia via Antarctica during the warm early Cenozoic. Keywords: wood anatomy, early Eocene, Huitrera Formation, Winteraceae, Winteroxylon, Zygogynum s.l. clade. teraceae is strongly supported in several molecular analyses (Suh et al. 1993; Qiu et al. 1999, 2005; Zanis et al. 2003; Soltis and Soltis 2004; Marquínez et al. 2009; Massoni et al. 2015a, 2015b; Müller et al. 2015; APG IV 2016). Both families are made up of aromatic woody shrubs and small trees with disjunct distributions in the Southern Hemisphere (Marquínez et al. 2009; Thomas et al. 2014). Today, the Winteraceae include ca. 60–90 species of evergreen trees, shrubs, and, rarely, epiphytes. Vink (1985) and Marquínez et al. (2009) recognized ﬁve extant genera within Winteraceae: Drimys J.R. Forst. & G. Forst, Pseudowintera Introduction The early-diverging angiosperm clade Magnoliidae comprises four orders: Magnoliales, Laurales, Canellales, and Piperales (Massoni et al. 2014, 2015a, 2015b; APG IV 2016). Canellales is the smallest magnoliid order and includes only the Canellaceae and Winteraceae. The sister relationship of Canellaceae and Win1 Author for correspondence; email: cidmbrea@gmail.com. Manuscript received August 2020; revised manuscript received October 2020; electronically published February 8, 2021. 000 000 INTERNATIONAL JOURNAL OF PLANT SCIENCES Dandy, Tasmannia R. Br. ex DC., Takhtajania Baranova & J. Leroy, and Zygogynum Baill. Vink (1988) later recognized four genera within Zygogynum s.l.: Bubbia Tiegh., Belliolum Tiegh., Exospermum Tiegh., and Zygogynum. Thomas et al. (2014) also recognized those four genera as a monophyletic group. Winteraceae and Canellaceae are each monophyletic (Massoni et al. 2014 and references cited therein), and several phylogenetic analyses agree that within the Winteraceae, Takhtajania is the earliest-diverging lineage (Marquínez et al. 2009; Massoni et al. 2014; Thomas et al. 2014; Müller et al. 2015; Grímsson et al. 2018), followed by Tasmannia and Drimys. All the preceding are collectively sister to a clade comprising Pseudowintera as sister to Zygogynum s.l. (including Belliolum, Bubbia, Exospermum, and Zygogynum s.s.; as proposed earlier by Vink 1988). The relationships within Zygogynum s.l. are not fully resolved (Grímsson et al. 2018). Marquínez et al. (2009) estimated the divergence of Takhtajania from the rest of the family to be at ca. 91.5 (120–74) Ma and indicated that Tasmannia may have diverged from other Winteraceae at ca. 69.9 (74.8–66.9) Ma. The living Winteraceae species are restricted to Australasia, Malesia, Oceania, Madagascar, and South and Central America, primarily in rain forest environments but also in a diverse range of dry to wet tropical to temperate climatic regions (Lindley 1836; Vink 1988, 1993; APG IV 2016). On the basis of its fossil record, the early history of Winteraceae can be traced back to the Cretaceous to Eocene of both hemispheres, after which the range contracted southward (Doyle 2000; Grímsson et al. 2018). Several molecular phylogenetic hypotheses based on nuclear and plastid sequence data are generally consistent, indicating that the Winteraceae had a long and complex biogeographic history that is explained by a combination of vicariance, long-distance dis- persal, and extinction events (Marquínez et al. 2009; Thomas et al. 2014). The living genera are considered typical members of the austral ﬂora (Thomas et al. 2014) and have disjunct distributions in Australasia and Malesia (Tasmannia, Pseudowintera, Zygogynum, Exospermum, Bubbia, Belliolum), Madagascar (Takhtajania), and the Neotropics (Drimys; Grímsson et al. 2018). This article reports a new fossil of Winteraceae from South America consisting of a large stump sampled at the early Eocene Laguna del Hunco (LH) fossil site in the Huitrera Formation, Chubut Province, Argentina (ﬁg. 1). The LH biota was ﬁrst studied by Berry (1925) and was sporadically investigated over the ensuing decades (e.g., Frenguelli 1943; Romero et al. 1988). Extensive research during the past 20 years has yielded extremely diverse ﬂora and fauna from the fossil caldera lake beds (for summaries, see, e.g., Wilf et al. 2013; Barreda et al. 2020; RossettoHarris et al. 2020), which are highly informative for understanding past and current biogeographical patterns in the Southern Hemisphere. The extensive biogeographic links of the LH ﬂora include, via ancient Gondwana, living rain forests of Australasia and Malesia, where the largest number of “survivor” genera are found in Australian and New Guinean lower montane rain forest ﬂoras (e.g., Zamaloa et al. 2006; Wilf et al. 2009; Gandolfo et al. 2011; Carvalho et al. 2013; Gandolfo and Hermsen 2017; Andruchow-Colombo et al. 2019). Nearly all reported plant fossils from LH are compressions (but see Barreda et al. 2020 for a diverse palynoﬂora), although decades ago, Petersen (1946) found fossilized trunks at the top of the main lake bed sequence that were not further studied. Permineralizations, including a siliciﬁed trunk of the fern Todea Willd. ex Bernh. (Osmundaceae) with in situ liverworts, fungi, and coprolites from the same source unit (Tufolitas LH) south Fig. 1 Distribution of extant (dark gray) and fossil (light gray, Cretaceous; black, Cenozoic; star, pollen; circle, wood; rectangle, leaf ) Winteraceae. Fossil wood records are labeled as follows: Winteroxylon mundlosi (late Eocene; Helmstedt Formation, Lower Saxony, Germany), Winteroxylon jamesrossi (early Campanian; Santa Marta Formation, James Ross Island, Antarctica), Winteroxylon? (Maastrichtian; Great Valley Sequence, California), Winteroxylon oleiferum sp. nov. (arrow; early Eocene; Laguna del Hunco, Huitrera Formation, Chubut Province, Argentina). Modiﬁed from Grímsson et al. (2018). References: Doyle (2000); Barreda and Archangelsky (2006); Marquínez et al. (2009); Grímsson et al. (2018); Liang et al. (2018); and others cited therein. BREA ET AL.—FIRST SOUTH AMERICAN RECORD OF WINTEROXYLON of the main LH exposures (Bippus et al. 2019; Bomﬂeur and Escapa 2019), have only recently been described from the area. Pujana et al. (2020) described a podocarp-dominated conifer wood assemblage from LH that included Protophyllocladoxylon francisiae Pujana, Santillana & Marenssi, Phyllocladoxylon antarcticum Gothan, and cf. Cupressinoxylon sp. 1 and sp. 2. In this article, we describe the ﬁrst fossil angiosperm wood from LH, a new species of Winteraceae, based on anatomical study of a siliciﬁed stump. On the basis of anatomical comparisons with extant and fossil specimens, we describe and interpret the signiﬁcance of the new species with regard to the wood evolution, fossil record, and biogeography of Winteraceae. Material and Methods The sample studied here was collected at LH, Huitrera Formation, by A. Iglesias and P. Wilf during the November 2009 ﬁeld season at lat. 42727036.2600S, long. 7072017.8600W, elevation 1109 m (ﬁg. 1). The stump was found lying in a horizontal position on a steep east-facing slope exposure of the fossiliferous LH caldera lake beds (Tufolitas LH; ﬁg. 2) at a position above the highest productive levels for compression fossils (i.e., quarry LH6; Wilf et al. 2003). The Tufolitas LH are well dated from 40 Ar/39Ar analyses of minerals in three different tuffs, all of them below the resting level of the trunk, and the presence of two paleomagnetic reversals (Wilf et al. 2003, 2005). A maximum sanidine 40Ar/39Ar age of 52:22 5 0:22 Ma for one tuff is considered most reliable (M. Smith in Wilf 2012) and provides a min- 000 imum age for the wood specimen. In addition, the youngest beds of the underlying local unit, the Ignimbrita Barda Colorada, have recently been 40Ar/39Ar dated as 52:54 5 0:17 Ma (Gosses et al. 2020). The Tufolitas LH, containing the new fossil, are overlain by the hill-capping (and completely unfossiliferous) Andesitas Huancache unit (Aragón and Mazzoni 1997). The Andesitas Huancache have not been dated locally using modern techniques, but potentially correlative strata in the southern caldera exposures have recently been 40Ar/39Ar dated to 49:19 5 0:24 Ma, providing a likely minimum age for the fossil lake beds (Gosses et al. 2020). Thus, the age of the wood specimen is early Eocene, with a possible age range of ca. 52.2–49.2 Ma. We prefer the older end of this range because of the provenance of the specimen in the Tufolitas LH (ca. 52.2 Ma radiometric age). The sampled stump is 150 cm in preserved length and 50 cm in diameter, increasing to 124 cm toward the base, with several woody roots of 4–15 cm in diameter that mostly have an axial orientation (ﬁg. 2B), although some broad roots are perpendicular to the main stem (ﬁg. 2B). Secondary wood from the distal part of the base of the main stem (ﬁg. 2C) was sampled, leaving the bulk of the specimen intact at the site. The siliciﬁed trunk has well-preserved secondary xylem. Thin sections were made using standard petrographic techniques (transverse, tangential longitudinal, and radial longitudinal). The anatomical terms used in this article follow the International Association of Wood Anatomists’ “List of Microscopic Features for Hardwood Identiﬁcation” (IAWA Committee 1989). The taxonomic assignment, descriptions, and comparisons with extant and fossil species were Fig. 2 A, Panoramic view of Eocene strata at Laguna del Hunco (LH), looking southwest from the LH4 fossil locality and showing the positions of selected fossil plant localities. Location of the Winteraceae fossil stump sampled here (1) and fossil locality LH4 (2; Wilf et al. 2003). B, Fossil stump in basal view, showing roots at the base of the stump (the black arrow indicates roots disposed perpendicular to the main stem; the white arrow indicates roots disposed in an axial orientation). C, Lateral view of the stump, clearly showing the two regions: the stump with roots (left) and the base of the main stem (right). D, View from the apical part of the preserved stem, showing the variation in the stump’s diameter toward the base. Pick for scale p 30 cm. 000 INTERNATIONAL JOURNAL OF PLANT SCIENCES performed following the InsideWood website (InsideWood 2004–; Wheeler 2011) and previous descriptions by Bailey and Thompson (1918), Bailey (1944), Bailey and Swamy (1948), Metcalfe and Chalk (1950), Swamy and Bailey (1950), Tortorelli (1956), Patel (1974), Carlquist (1981, 1982, 1983a, 1983b, 1987, 1988, 1989, 2000, 2001), Scott and Wheeler (1982), Rancusi et al. (1987), Poole and Francis (2000), Carlquist and Schneider (2001), and Schweingruber et al. (2011). The specimen was studied with a Nikon Eclipse E200 light microscope, and photomicrographs were taken with an attached Nikon Coolpix S4 digital camera. The values in the anatomical description are averages of 25 measurements. In all cases, the average value is cited ﬁrst, followed by the minimum and maximum values, which are given in parentheses. We prepared the specimen for scanning electron microscopy (SEM) by cutting 1-cm3 blocks of fossil wood, mounting them on SEM stubs, and coating them with platinum/palladium; observation and photographs were done using an FEI Nova NanoSEM 230 microscope at the Laboratorio de Microscopía, Caracterización de Materiales, Centro Atómico Bariloche, Argentina. The macrofossil specimens and slides are deposited at the Museo Paleontológico Egidio Feruglio paleobotanical collection (MPEF-Pb) in Trelew, Argentina. Results Systematic Paleobotany Order—Canellales Family—Winteraceae Genus—Winteroxylon (Gottwald) emend. Poole & Francis 2000 Fig. 3 Winteroxylon oleiferum sp. nov., MPEF-Pb 3997. A, General view in transverse section, showing uniseriate rays (arrows) and tracheids. B, C, General view in transverse section, showing uniseriate rays (white arrows), multiseriate rays (black arrows), and tracheids. D, General view in tangential longitudinal section, showing uniseriate and multiseriate rays (white arrow) composed of procumbent and upright cells and probable sheath cells (black arrows). E, F, General view in tangential longitudinal section, showing oil cavities (arrows) surrounded by parenchymatic cells inside the multiseriate rays. G, General view in tangential longitudinal section, showing sclerotic nests (white arrow) and dark amorphous contents (black arrow) in a multiseriate ray. H, I, General view in radial longitudinal section, showing heterocellular rays composed of procumbent and upright cells (arrows). Scale bars p 400 mm. BREA ET AL.—FIRST SOUTH AMERICAN RECORD OF WINTEROXYLON Type Species—Winteroxylon mundlosi Gottwald 1992 Species—Winteroxylon oleiferum Brea, Iglesias, Wilf, Moya & Gandolfo sp. nov. (Figs. 3–6) Etymology. The speciﬁc name refers to the abundance of oil cells in the wood. Speciﬁc diagnosis. Growth rings indistinct. Tracheids thick walled with circular bordered pits, mainly in uniseriate, biseriate, and triseriate rows, alternate to opposite. Axial parenchyma either diffuse or in tangentially or radially oriented pairs of parenchyma strands. Rays of two different types (narrow and broad), heterocellular and very tall, uniseriate, biseriate, and multiseriate (3–15 cells wide). Bordered pits in ray cells. Sclerotic nests, oil cells, and dark contents in rays present. 000 Holotype. MPEF-Pb 3997a–MPEF-Pb 3997e (one macrofossil and four microscope slides). Locality. LH, early Eocene of northwestern Chubut Province, Argentina (lat. 42727036.2600S, long. 707 2017.8600W), Huitrera Formation. Description. The description is based on the mature wood of one stump specimen. In transverse section, the mature wood is vesselless and composed exclusively of imperforate tracheids and parenchyma (ﬁgs. 3A–3C, 4A), with indistinct growth rings (ﬁg. 3A–3C). The tracheids are quadrangular to rectangular (ﬁgs. 4A, 4D, 5E) and have a mean tangential diameter of 24 (14–33) mm and a mean radial diameter of 27 (19–31) mm. They are thick walled (ﬁg. 5E), with a wall thickness of 7 (5–9) mm. Middle lamellae and pits are observed on the tracheids (ﬁg. 5E). Triangular or quadrangular intercellular spaces (ﬁg. 4A, 4D) Fig. 4 Winteroxylon oleiferum sp. nov., MPEF-Pb 3997. A, Detail in transverse section, showing tracheids, axial parenchyma (arrows), and a multiseriate ray. Scale bar p 200 mm. B, Detail in tangential longitudinal section, showing multiseriate, biseriate (black arrow), and uniseriate (white arrow) rays. Scale bar p 200 mm. C, Detail in tangential longitudinal section, showing multiseriate rays of up to 15 cells. Scale bar p 200 mm. D, Detail in transverse section, showing axial parenchyma with pits (arrows). Scale bar p 50 mm. E, Detail of a parenchyma pit in transverse section (arrow). Scale bar p 20 mm. F, Detail in tangential longitudinal section, showing a sclerotic nest. Scale bar p 200 mm. G, Detail in radial longitudinal section, showing a heterocellular ray composed of procumbent and upright cells. Scale bar p 200 mm. H, Detail in tangential longitudinal section, showing an oil canal (arrow). Scale bar p 200 mm. I, Detail in tangential longitudinal section, showing the dark contents in a ray cell. Scale bar p 50 mm. J, General view in radial longitudinal section, showing the bordered pits in the ray cells (arrow). Scale bar p 200 mm. K, Detail in radial longitudinal section, showing the bordered pit in a ray cell (arrow). Scale bar p 50 mm. 000 INTERNATIONAL JOURNAL OF PLANT SCIENCES Fig. 5 Winteroxylon oleiferum sp. nov., MPEF-Pb 3997. A, Detail in tangential longitudinal section, showing circular bordered and uniseriate pits. Scale bar p 20 mm. B, Detail in tangential longitudinal section, showing circular bordered, biseriate, and alternate pitting. Scale bar p 50 mm. C, Detail in tangential longitudinal section, showing circular bordered, triseriate, and alternate to opposite pitting. Scale bar p 50 mm. D, Detail in tangential longitudinal section, showing a biseriate ray and trabeculae in the tracheids (arrows). Scale bar p 50 mm. E, Detail in transverse section, showing three tracheid cells with middle lamellae (white arrow) and a pit (black arrow). Scale bar p 20 mm. F, Detail in radial longitudinal section, showing bordered pits that are alternate to irregular in arrangement (arrow) in the ray cells. Scale bar p 50 mm. G, Detail in tangential longitudinal section, showing sclerotic cells (white arrow) and dark amorphous accumulations in a cell (black arrow). Scale bar p 50 mm. H, Detail in tangential longitudinal section, showing a sclerotic nest. Scale bar p 50 mm. are present between tracheids. The axial parenchyma is diffuse and scarce, presenting as occasional radially oriented pairs of parenchyma strands (ﬁg. 4A, 4D). The parenchyma cell pits are small, circular, and simple (ﬁg. 4D, 4E). In tangential longitudinal section, the tracheid pitting is circular, bordered, and contiguous, with elliptic pit apertures (ﬁg. 5A– 5C). The circular pits have a mean diameter of 8 (7–10) mm and are frequently uniseriate (ﬁg. 5A), occasionally biseriate (ﬁgs. 5B, 6C), and rarely triseriate (ﬁg. 5C); when bi-triseriate. pits are alternate to opposite. Some tracheids have trabeculae on their walls (ﬁg. 5D). The rays are of two distinct types, uniseriate-biseriate and multiseriate (3–15 cells), and both are heterocellular and Fig. 6 Winteroxylon oleiferum sp. nov., MPEF-Pb 3997, under scanning electron microscopy. A, Detail in radial longitudinal section, showing bordered pits in ray cells that are alternate to irregular in arrangement. Scale bar p 100 mm. B, Detail in radial longitudinal section, showing bordered pits. Scale bar p 30 mm. C, Detail in tangential longitudinal section, showing biseriate, bordered, and alternate to opposite pits in a tracheid. Scale bar p 30 mm. BREA ET AL.—FIRST SOUTH AMERICAN RECORD OF WINTEROXYLON composed of predominantly upright cells (ﬁgs. 3I, 4G), occasionally with procumbent cells (ﬁgs. 3I, 4F). The sclerotic nests (ﬁgs. 3G, 4F, 5H), sclereids (ﬁg. 5G), and oil cells (ﬁgs. 3E–3F, 4H) are abundant and are associated with ray parenchyma. The oil cells are similar to the parenchyma cells in size and are found scattered in rays; oil cavities are occasionally present in the central portions of multiseriate rays and are surrounded by three or more layers of parenchyma cells (ﬁgs. 3E–3F, 4H). Sclereid cells are polygonal or hexagonal in outline (ﬁgs. 4F, 5G, 5H), with a diameter of 99 (43–178) mm, and are thick walled, with a wall thickness of 34 (8–64) mm (ﬁg. 5H). Each sclerotic nest has 3–11 sclereid cells. The multiseriate rays have a mean height of 2089 (1035–4105) mm and a mean width of 547 (188–1504) mm. Probable sheath cells occur in the multiseriate rays (ﬁg. 3D). The uniseriate (ﬁg. 4B) and biseriate (ﬁg. 4B) rays (86%) are more common than the multiseriate rays (14%; ﬁgs. 3D–3G, 4A–4C). The uniseriate rays are heterocellular and have a mean height of 314 (131–655) mm and a mean width of 35 (23–55) mm. In both ray types (narrow and broad), dark amorphous contents are observed inside the ray cells, probably attributable to resins (ﬁgs. 3G, 4I, 5G). In radial longitudinal section, the tracheid pitting is more abundant on the radial compared with the tangential walls (ﬁg. 4J). The rays are heterocellular, composed of upright and procumbent cells (ﬁg. 4G). The ray cell pits are circular, bordered, and alternate to irregular in arrangement (ﬁgs. 4K, 5I, 6A, 6B). The procumbent cells are 97 (73–154) mm in height and 26 (16–35) mm in width, and upright cells are 51 (43–58) mm in height and 32 (22–38) mm in width. Discussion Comparison with Extant and Fossil Taxa The absence of the typical conifer cross-ﬁeld pitting and the presence of heterocellular uni- to multiseriate rays, axial parenchyma, cells with contents (i.e., oil cells, idioblasts), and sclereids conﬁrm that this fossil corresponds to a vesselless angiosperm. Vesselless woods are present in ﬁve early-diverging angiosperm families: Amborellaceae, Tetracentraceae, Trochodendraceae, Chloranthaceae, and Winteraceae (Bailey and Thompson 1918; Bailey 1944; Bailey and Swamy 1948; Metcalfe and Chalk 1950; Swamy and Bailey 1950; Carlquist 1987; Schweingruber et al. 2011). Amborella trichopoda Baill. is the only known member of Amborellaceae; it is endemic to New Caledonia, inhabiting the understory of humid forests, where it grows as shrubs or small trees. Its wood is characterized by vesselless xylem with very weakly deﬁned growth rings, bordered circular and scalariform pits on the tracheids, diffuse apotracheal axial parenchyma, dark contents in parenchyma cells, uniseriate and multiseriate (up to ﬁve cells) rays, and heterocellular rays with more than four marginal upright cells (Carlquist and Schneider 2001; Schweingruber et al. 2011). This extant species differs from the new fossil specimen in having multiseriate rays that are three to ﬁve cells wide, scalariform pits on the tracheids, and rays with more than four marginal upright cells. Tetracentraceae, native to southern China and the eastern Himalayas, includes the sole extant species Tetracentron sinense Oliv. It grows along streams or forest margins in broad-leaved evergreen forests and mixed evergreen-deciduous forests (Suzuki et al. 1991) as trees that can reach up to 40 m tall. The secondary 000 xylem is characterized by having axial parenchyma that is diffuse and diffuse in aggregates and uniseriate and homocellular multiseriate rays that are three or four cells wide (Poole and Francis 2000; InsideWood 2004–). Tetracentron differs from the fossil and extant Winteraceae woods in having rays that are three or four cells wide and exclusively procumbent cells. Also, Tetracentron has unusual thin-walled tracheids arranged in radial ﬁles, with crowded, alternate, circular to elliptical bordered pits in the tangential walls and radial walls without pitting (Suzuki et al. 1991); all of these features are unlike those of the new fossil. Trochodendron aralioides Sieb. & Zucc. belongs to the monospeciﬁc Trochodendraceae. They are evergreen trees or large shrubs growing up to 20 m tall that are conﬁned to montane temperate forests in Southeast Asia and Taiwan (APG IV 2016). Their secondary xylem has distinct growth rings, bordered scalariform pit tracheids, axial parenchyma that is rare or absent, and rays in two types: uniseriate and heterocellular multiseriate, three to six cells wide. There are large and simple pits in the ray cells (Schweingruber et al. 2011). Trochodendron differs from the new Patagonian taxon in having distinct growth rings, axial parenchyma that is absent or extremely rare, bordered scalariform pits in the tracheids, simple pits in the cell rays, and multiseriate rays with very tall uniseriate extensions (Scott and Wheeler 1982; Richter and Dallwitz 2000). Sarcandra Gardner, the only vesselless genus within the Chloranthaceae, includes small shrubs native to Southeast Asia; its wood has distinct growth rings, absent or rare axial parenchyma, tracheids and transitional tracheid-vessel elements, and, commonly, 4–10 seriate heterocellular rays (Swamy and Bailey 1950; Carlquist 1987; InsideWood 2004–). Sarcandra has fascicular uniseriate rays and interfascicular multiseriate rays. These large multiseriate (up to ﬁve cells wide) parenchyma rays in Sarcandra are derived from a cambial variant that produces axial vascular elements in segments and interfascicular multiseriate rays (Pipo et al. 2020). Cambial variant features are absent in Winteroxylon oleiferum sp. nov. Of all these vesselless angiosperms, only Winteraceae have woods with 110-seriate rays, oil cells, and sclerotic nests in heterocellular rays, as seen in the fossil. The new fossil species shares additional character states with Winteraceae, including absent growth rings, tracheids that are rectangular in transverse section with circular bordered pits, diffuse axial parenchyma, rays of two distinct sizes, uniseriate-biseriate and multiseriate (3–15 cells wide) rays, and cells with dark contents. We summarize the anatomical comparison between the new fossil species and the extant species of Winteraceae (table 1). Clearly, the new Patagonian fossil species is most similar to the extant species in the Zygogynum s.l. clade (Bubbia, Belliolum, Exospermum, and Zygogynum s.s.). The extant genera Pseudowintera, Takhtajania, and Belliolum are different from the new Patagonian species in their absence of oil cells, silica bodies, and sclerotic nests. The American genus Drimys does not produce oil cells or sclerotic nests and has smooth and irregular silica bodies, a feature absent in the fossil wood. Tasmannia differs in having uniseriate and biseriate radial tracheid pits with helical thickenings and rays that do not have oil cells. Exospermum lacks sclerotic nests in rays and has rectangular tracheids in transverse section and axial parenchyma in bands. Zygogynum s.s. differs because it has uniseriate tracheid pitting and an absence of trabeculae in the tracheids (table 1). On the other hand, Bubbia shares Table 1 Wood Anatomical Comparisons of Winteroxylon oleiferum sp. nov. with Extant and Fossil Taxa of Winteraceae Taxon Drimys Takhtajania Tasmannia Tracheid section Square to irregular Bubbia Exospermum Uniseriate, biseriate, triseriate Tracheid diameter (mm)a Tracheid pitting 6–16 mm in diameter, circular, bordered, opposite, alternate, scalariform Quadrangular Uniseriate, biseriate; 38 (mean) Circular, bordered, to rectangular helical thickenings scalariform Quadrangular Uniseriate, biseriate; to rectangular helical thickenings Pseudowintera Square to irregular Belliolum Radial tracheid pitting Quadrangular to rectangular Uniseriate, biseriate, triseriate; spiral thickenings and trabeculae Biseriate, triseriate 25–69 16–46 Circular, bordered, scalariform to transitional 13–46 Circular, bordered, alternate, opposite, scalariform Circular, bordered, scalariform to transitional to opposite Square to Uniseriate, biseriate, 23–51 7–14 mm in diameter, irregular triseriate; trabeculae circular, opposite, common occasionally elongated, scalariform Quadrangular Biseriate, triseriate 55 (mean) Circular to elongated, to rectangular alternate Uniseriate 42–60 Zygogynum s.s. Square to irregular ... W. oleiferum sp. nov. 14–33 Quadrangular Uniseriate, biseriate, to rectangular triseriate; trabeculae common Circular, bordered, scalariform 7–10 mm in diameter, circular, alternate to opposite Winteroxylon mundlosi ... Uniseriate, biseriate; sometimes scalariform 23–36 Circular Winteroxylon jamesrossi ... Uniseriate, biseriate; elongate to scalariform 30–50 Circular to more elongate a Tracheid diameter is measured in tangential section. Axial parenchyma Ray type and structure Scarce or absent, diffuse Ray height (mm) Uniseriate, multiseriate (4–10 cells), heterocellular Scarce, diffuse Uniseriate, biseriate, multiseriate (up to 5 cells), heterocellular Scarce, diffuse, occa- Uniseriate, biseriate, sional tangential or multiseriate, radial parenchyma heterocellular strands Scarce, diffuse, diffuse Uniseriate, biseriate, in aggregates multiseriate (7–29 cells), heterocellular Scarce, diffuse, in Heterocellular short bands Uniseriate (300– 3370), multiseriate (1250–4800) Uniseriate (mean, 1473), multiseriate (mean, 4176) Uniseriate (286– 1816), multiseriate (1093–5148) Uniseriate, multiseriate (300–6100) Diffuse or in bands 1–3 cells thick Uniseriate, biseriate, multiseriate (3–7 cells), heterocellular Diffuse or in bands Uniseriate, 1–3 cells thick multiseriate (up to 7 cells) Scarce, diffuse, diffuse Uniseriate, in aggregates, in multiseriate bands 2 or 3 cells thick Scarce, diffuse, occa- Uniseriate, biseriate, multiseriate sional tangential or (3–15 cells), radial parenchyma strands heterocellular Uniseriate bands Uniseriate, multiseriate (3–7 cells), heterocellular Diffuse or in radial Uniseriate, biseriate, pairs and short multiseriate strands of up to (3–13 cells), ca. 4 cells thick heterocellular Cell contents Oil cells Sclerotic nest Dark Absent Absent amorphous Tannin-like ... Absent Absent Absent Present Absent Absent Absent Resinlike Absent Absent 600 to 11500 Resinlike Present Absent Multiseriate (mean, 6812) Resinlike Present Absent ... ... ... Present Sclereids Uniseriate (131–665), multiseriate (1035–4105) All rays higher than 2000 Dark Present Present amorphous Present Absent Present Uniseriate (200–1636), multiseriate (500–4300) Occasional Absent Absent BREA ET AL.—FIRST SOUTH AMERICAN RECORD OF WINTEROXYLON with W. oleiferum sp. nov. the uniseriate, biseriate, and triseriate arrangement of tracheid pitting in the radial walls, the presence of trabeculae in the tracheids, square to irregular tracheids in transverse section, and oil cells associated with the rays. Winteroxylon oleiferum sp. nov. is placed in Winteroxylon based on the presence of indistinct growth rings, predominantly diffuse axial parenchyma, tracheids with circular bordered pits, and predominantly multiseriate rays with up to 13 cells or uniseriate-biseriate rays that are heterocellular and nonstoried (Poole and Francis 2000). All of the features of the new fossil ﬁt within Winteroxylon, and thus there is no basis for erecting a new genus. Until now, there were only two reliable fossil woods assigned to the Winteraceae, Winteroxylon jamesrossi Poole & Francis from the early Campanian Santa Marta Formation, Antarctic Peninsula (Poole and Francis 2000; Olivero 2012; ﬁg. 1), and Winteroxylon mundlosi Gottwald from the late Eocene Helmstedt Formation, lignite opencast mine, Lower Saxony, Germany (Gottwald 1992; ﬁg. 1). Winteroxylon jamesrossi lacks the oil cells and sclerotic cells seen in the new fossil, whereas W. mundlosi differs from the Patagonian fossil in having taller rays and an absence of oil cells (table 2). Also, both of 000 the previously known Winteroxylon species have distinct scalariform tracheid pitting not seen in the new species. Page (1979, 1981) described a minute (7 mm in diameter) twig of putative Winteraceae afﬁnity from the Maastrichtian Great Valley Sequence (California; ﬁg. 1) that can be easily distinguished from the new fossil because of its abundant axial parenchyma, absence of bi-triseriate rays, and absence of both oil cells and sclerotic cells (table 2). According to Poole and Francis (2000), the anatomical characters of W. jamesrossi are related to those exhibited in extant Bubbia. However, as also noted by those authors, there are many differences between the extant genus and the Antarctic fossil. It seems clear that W. jamesrossi most closely matches anatomically with extant Takhtajania and Tasmannia, especially in ray height, the type of tracheid pitting, and the absence of both trabeculae and oil cells (table 1). Winteroxylon mundlosi has a central pith with sclerotic cells, rays greater than 2 mm in height and up to eight cells wide, and sclerotic cells (table 2). Although Gottwald (1992) did not identify oil cells in W. mundlosi, they were noted as possibly present in this taxon by Poole and Francis (2000). Gottwald (1992) Table 2 Further Comparison among Fossil Wood Species of Winteraceae Winteroxylon jamesrossi Reference(s) Fossil locality Stratigraphic horizon, age Growth rings Axial parenchyma Tracheids: Tangential diameter (mm) Radial diameter (mm) Wall thickness (mm) Pitting diameter (mm), shape Overlapped area Rays: Structure Height (mm) Width Cell pitting Cell content: Dark amorphous Oil cells Sclerotic cells Winteroxylon mundlosi Winteroxylon? Winteroxylon oleiferum sp. nov. Poole and Francis 2000 Lachman Crags, James Ross Island, Antarctica Santa Marta Formation, early Campanian Indistinct Diffuse or in radial pairs; forms short axial strands of up to 4 cells Gottwald 1992 Helmstedt area, Lower Saxony, Germany Annenberg Formation, late Eocene Indistinct Uniseriate bands or in tangential, apotracheal, uniseriate bands Page 1979, 1981 Diablo Range, central California Great Valley Sequence, Maastrichtian ? Abundant This contribution Laguna del Hunco, Chubut, Argentina La Huitrera Formation, early Eocene Indistinct Diffuse, occasional tangentially or radially oriented strand pairs 30 (35) 50 23 (29) 36 13 (26) 38 14 (24) 33 15 (28) 40 2.5–10 2.5–15, circular to more elongate Uniseriate, biseriate, elongate to scalariform ... 5 (7) 9 7 (9) 11, circular ... Thick walled Small, rounded 19 (27) 31 5 (7) 9 7 (8) 10, circular Heterocellular procumbent cells becoming square to periphery; upright cells in uniseriate and multiseriate wings Uniseriate, 200–1636; multiseriate, 500–4300 Uniseriate, biseriate; 4–13 cells Circular, bordered Heterocellular upright cells in uniseriate and multiseriate wings Circular Uniseriate, 131 (314) 655; multiseriate, 1035 (2089) 4105 Uniseriate, multiseriate; Uniseriate, biseriate; 4–5 cells 3–15 cells Minute pits on tangential walls Circular, bordered Occasional Absent Absent Present Absent Present Absent? Absent Absent Uniseriate, biseriate, sometimes scalariform All rays greater than 2000 Uniseriate; 3–8 cells ? Heterocellular square or upright cells Uniseriate, biseriate, triseriate Heterocellular upright and procumbent cells ? Present Present Present INTERNATIONAL JOURNAL OF PLANT SCIENCES 000 placed W. mundlosi as closely related to extant Drimys and Bubbia. In table 1, the European fossil matches most closely with extant Takhtajania and Tasmannia. On the basis of this discussion, W. oleiferum sp. nov. may represent the sole fossil sharing wood anatomy with the Zygogynum s.l. clade (following Thomas et al. 2014). Sherwinoxylon winteroides Boura & Saulnier, a vesselless angiosperm of uncertain family from the middle Cenomanian of the Envigne Valley in western France, has exclusively multiseriate rays up to nine cells wide and 1.03–10.53 mm high that are composed of square cells, as well as up to four upright marginal cells. This fossil shows similarities to extant and fossil Winteraceae, but the absence of uniseriate rays led Boura et al. (2019) to suggest that it may belong to an extinct group that either is unrelated to Winteraceae or belongs to stem Winteraceae. Sherwinoxylon winteroides also differs from W. oleiferum sp. nov. in having tracheids with exclusively uniseriate bordered pits and an absence of uniseriate rays, oil cells, and sclerotic cells. Biogeography and Phylogenetic Relationships of Winteraceae The living genera of Winteraceae have disjunct distributions in Australasia (Pseudowintera, Zygogynum, Exospermum, Bubbia, Belliolum, Tasmannia), Madagascar (Takhtajania), and the Neotropics (Drimys; e.g., Grímsson et al. 2018). The habit and geographical distribution of the extant genera of Winteraceae are shown in table 3. Winteraceae has fossil records from the Cretaceous in Laurasia and Gondwana, suggesting that the group was globally distributed from the Cretaceous until at least the Eocene in the Northern Hemisphere and that it subsequently became extinct (Grímsson et al. 2018). In the Southern Hemisphere, this family has been a persistent component of rain forests or wet sclerophyll forests (Hill 1994; Marquínez et al. 2009), with records since the middle Cretaceous (Barreda and Archangelsky 2006; ﬁg. 1). In addition to the Winteraceae fossil wood record (table 2), pollen tetrads of Walkeripollis gabonensis Doyle, Hotton & Ward were reported from the Barremian-Aptian of Gabon, Africa (Doyle et al. 1990; ﬁg. 1). Qatanipollis valentini Schrank is a putative Winteraceae pollen type described from the late AptianAlbian of Israel (Schrank 2013) that was originally reported by Walker et al. (1983) and then designated by Doyle et al. (1990) as Walkeripollis sp. In Australasia, the fossil record of this family dates from mid-Campanian sediments of the Otway Basin (Dettmann and Jarzen 1990; Grímsson et al. 2018). Grímsson et al. (2018) proposed that Winteraceae pollen fossils recorded in the Paleocene and Eocene of North America and Greenland represent interchange with Europe via the North Atlantic land bridge. This hypothesis could also explain the presence of Winteraceae woods in California and Germany (ﬁg. 1; table 2). Reliable leaf fossils of Winteraceae are very rare (ﬁg. 1). Zygogynum poratus Liang & Zhou is a leaf compression from the middle Miocene of Yunnan, southwest China, that shares cuticular features and morphological characters with Zygogynum s.s. (Liang et al. 2018). A leaf impression assigned to Drimys Table 3 Comparison of the Stem Morphologies, Habit Preferences, Phenology, Habits, and Geographic Distributions of the Genera of Winteraceae Stem diameter Stem height (cm) (m) Growth habit Drimys Takhtajania .6–10 Up to 20 Shrubs to small trees Evergreen Up to 4.5 Up to 5 Shrubs to small trees Small trees Evergreen 4–34 Tasmannia Leaf habit 4 or more Evergreen Habitat Moist mountain forests (tropical and temperate, frost-free) in Neotropics, maritime temperate rain forests, subantarctic temperate forests Subhumid higher montane forests (~1000 m) Moist mountain forests, in wet areas in the drier forests, alpine and lowland temperate rain forests Lowland to higher montane forests (from lat. 357S to 427S) Pseudowintera 2.5–6.6 1–8 Shrubs to small trees Evergreen Zygogynum s.l. clade: Belliolum ca. 10 ... Small trees Evergreen ... 15 Small to large Evergreen trees Understory and subcanopy treeless to trees in subtropical lowland rain forests Tropical premontane and montane cloud forests Exospermum ca. 24 ... Large trees Subtropical lowland rain forests Zygogynum s.s. ... 2–3 Small trees to Evergreen shrubs Bubbia Sources. Evergreen Subcanopy trees in subtropical lowland rain forests and montane cloud forests Extant geographic distribution Neotropics (from southern Mexico to southern South America) Madagascar Australia, New Guinea, Celebes, Borneo, Philippines New Zealand Solomon Islands, New Caledonia Eastern Australia, New Guinea, New Caledonia, Moluccas Eastern Australia, New Guinea, New Caledonia, Moluccas New Caledonia Tortorelli (1956); Patel (1974); Carlquist (1981, 1982, 1983a, 1983b, 1988, 1989, 2000); Feild et al. (2000). BREA ET AL.—FIRST SOUTH AMERICAN RECORD OF WINTEROXYLON antarctica Dusén from the Cross Valley Formation, Seymour Island, Antarctic Peninsula, is poorly preserved and lacks diagnostic features that would provide a reliable taxonomic position within Winteraceae (Dusén 1908; Tosolini et al. 2013). In Patagonia, a leaf impression dubiously assigned to Drimys, Drimys patagonica Berry from the middle Eocene Río Pichileufú ﬂora (Berry 1938), Argentina, needs further study to clarify its taxonomic status. The oldest occurrence of Winteraceae pollen in South America was dated to the late Albian-Cenomanian Kachaike Formation (Barreda and Archangelsky 2006; ﬁg. 1). From the Paleogene, Pseudowinterapollis couperi (Krutzsch) emend. Mildenhall & Crosbie pollen grains were recovered from Argentine Patagonia in the late Eocene Sloggett Formation (Olivero et al. 1998), the late Oligocene?–Miocene Chenque Formation (Barreda 1997b), and the Oligocene San Julián Formation (Barreda 1997a), among others (e.g., Kooyman et al. 2014). According to Doyle (2000), the sculpture and presence of a well-deﬁned annulus in the Oligocene P. couperi from the Chenque Formation could indicate production by plants closely related to Drimys, whereas Grímsson et al. (2018) proposed that the South American fossil pollen could be linked to the extant genera Drimys, Tasmannia, and Pseudowintera, along with the Miocene tetrad Pseudowinterapollis africanensis Grímsson, Neumann & Zetter of South Africa (Grímsson et al. 2017). As discussed above, W. oleiferum sp. nov. resembles members of the extant Zygogynum s.l. clade because it has distinctive sclerotic nests and oil cells. Furthermore, most of its anatomical characters, including the presence of uniseriate, biseriate, and triseriate tracheid pitting in the radial walls, trabeculae in tracheids, square to irregular tracheid transverse sections, and oil cells associated with ray cells, match those of extant Bubbia (table 1). Today, the Zygogynum s.l. clade is distributed in eastern Australia, New Guinea, the Moluccas, and New Caledonia and predominantly in tropical premontane and montane cloud forests (table 3), locations and environments that are well identiﬁed for having large numbers of “survivor” taxa from the LH ﬂora and late-Gondwanan fossil ﬂoras in general (e.g., Wilf et al. 000 2009, 2013, 2019; Kooyman et al. 2014, 2019). The only previous fossil record assigned to the Zygogynum s.l. clade is Miocene leaves of Z. poratus from southwest China, indicating an additional past distribution of the clade, thought to be sourced from Gondwana, in mainland Asia (Liang et al. 2018). The phylogenetic analyses of Suh et al. (1993), Marquínez et al. (2009), and Thomas et al. (2014) show that the Zygogynum s.l. clade can be resolved into two subclades: the (Zygogynum 1 Belliolum 1 Exospermum) subclade from New Caledonia and the other with the Bubbia species, distributed in eastern Australia, New Guinea, the Moluccas, and New Caledonia (table 3). Thus, W. oleiferum sp. nov. is the oldest reliable macrofossil record of Winteraceae resembling species of the Zygogynum s.l. clade—a derived clade within extant Winteraceae—that today live in Australasian and Malesian rain forests. The presence of Bubbia-like Winteraceae at middle latitudes of Patagonia during the early Eocene reinforces the evidence for southern biogeographic connections between South America and Australasia via Antarctica during the warm early Cenozoic and the subsequent extinction of some Winteraceae clades in South America. Acknowledgments For exceptional assistance in the ﬁeld and laboratory, we are grateful to M. Caffa, L. Canessa, P. Puerta, and E. Ruigomez, and we thank the Nahueltripay family and the Secretaría de Cultura of the Chubut Province Government for land access. We thank Laboratorio de Microscopía, Grupo de Caracterización de Materiales, Centro Atómico Bariloche for SEM imaging, M. Medina from the LABGEO-Córdoba University (CICTERRA-CONICET) for making the petrographic sections, and two anonymous reviewers and Editor Alexandru M.F. Tomescu for helpful comments on the manuscript. We acknowledge ﬁnancial support from National Science Foundation grants DEB-0345750, DEB-0919071, DEB-0918932, DEB-1556666, DEB-1556136, EAR-1925755, and EAR-1925481. Literature Cited Andruchow-Colombo A, P Wilf, IH Escapa 2019 A South American fossil relative of Phyllocladus: Huncocladus laubenfelsii gen. et sp. nov. (Podocarpaceae), from the early Eocene of Laguna del Hunco, Patagonia, Argentina. Aust Syst Bot 32:290–309. APG IV (Angiosperm Phylogeny Group IV) 2016 An update of the Angiosperm Phylogeny Group classiﬁcation for the orders and families of ﬂowering plants: APG IV. Bot J Linn Soc 181:1–20. Aragón E, MM Mazzoni 1997 Geología y estratigrafía del complejo volcánico-piroclástico del Río Chubut medio (Eoceno). Rev Asoc Geol Argent 52:243–256. Bailey IW 1944 The comparative morphology of the Winteraceae. III. Wood. J Arnold Arbor 25:97–103. Bailey IW, BGL Swamy 1948 Amborella trichopoda Baill., a new morphological type of vesselless dicotyledon. J Arnold Arbor 29:245–253 Bailey IW, WP Thompson 1918 Additional notes upon the angiosperms Tetracentron, Trochodendron, and Drimys, in which vessels are absent from the wood. Ann Bot 32:503–512. Barreda VD 1997a Palinoestratigrafía de la Formación San Julián en el área de Playa de la Mina (provincia de Santa Cruz), Oligoceno de la Cuenca Austral. Ameghiniana 34:283–294. ——— 1997b Palynomorph assemblage of the Chenque Formation, late Oligocene?-Miocene from Golfo San Jorge Basin, Patagonia, Argentina. Ameghiniana 34:145–154. Barreda VD, S Archangelsky 2006 The southernmost record of tropical pollen grains in the mid-Cretaceous of Patagonia, Argentina. Cretac Res 27:778–787. Barreda VD, MC Zamaloa, MA Gandolfo, C Jaramillo, P Wilf 2020 Early Eocene spore and pollen assemblages from the Laguna del Hunco fossil-lake beds, Patagonia, Argentina. Int J Plant Sci 181:594–615. Berry EW 1925 A Miocene ﬂora from Patagonia. Johns Hopkins Univ Stud Geol 6:183–251. ——— 1938 Tertiary ﬂora from the Río Pichileufú, Argentina. Geol Surv Am Spec Pap 12:1–149 Bippus AC, IH Escapa, P Wilf, AMF Tomescu 2019 Fossil fern rhizomes as a model system for exploring epiphyte community structure across geologic time: evidence from Patagonia. PeerJ 7:e8244. Bomﬂeur B, I Escapa 2019 A siliciﬁed Todea trunk (Osmundaceae) from the Eocene of Patagonia. Palaontol Z 93:543–548. Boura A, G Saulnier, D De Franceschi, B Gomez, V Daviero-Gomez, D Pons, G Garcia, N Robin, J-M Boiteau, X Valentin 2019 An early 000 INTERNATIONAL JOURNAL OF PLANT SCIENCES record of a vesselless angiosperm from the middle Cenomanian of the Envigne Valley (Vienne, western France). IAWA J 40:530–550. Carlquist S 1981 Wood anatomy of Zygogynum (Winteraceae); ﬁeld observations. Adansonia 3:281–292. ——— 1982 Exospermum stipitatum (Winteraceae); observations on wood, leaves, ﬂowers, pollen and fruit. Aliso 10:277–289. ——— 1983a Wood anatomy of Belliolum (Winteraceae) and a note on ﬂowering. J Arnold Arbor 64:161–169. ——— 1983b Wood anatomy of Bubbia (Winteraceae) with comments on origin of vessels in dicotyledons. Am J Bot 70:578–590. ——— 1987 Presence of vessels in wood of Sarcandra (Chloranthaceae); comments on vessel origins in angiosperms. Am J Bot 74:1765–1771. ——— 1988 Wood anatomy of Drimys s.s. (Winteraceae). Aliso 12: 81–95. ——— 1989 Wood anatomy of Tasmannia; summary of wood anatomy of Winteraceae. Aliso 12:257–275. ——— 2000 Wood and bark anatomy of Takhtajania (Winteraceae); phylogenetic and ecological implications. Ann Mo Bot Gard 87:317– 322. ——— 2001 Comparative wood anatomy: systematic, ecological, and evolutionary aspect of dicotyledon wood. Springer Series in Wood Science. Springer, Berlin. Carlquist S, EL Schneider 2001 Vegetative anatomy of the New Caledonian endemic Amborella trichopoda: relationships with the Illiciales and implications for vessels origin. Pac Sci 55:305–312. Carvalho MR, P Wilf, MA Gandolfo, EJ Hermsen, KR Johnson, NR Cúneo 2013 First record of Todea (Osmundaceae) in South America, from the early Eocene paleorainforests of Laguna del Hunco (Patagonia, Argentina). Am J Bot 100:1831–1848. Dettmann ME, DM Jarzen 1990. The Antarctic/Australian rift valley: Late Cretaceous cradle of northeastern Australasian relicts? Rev Palaeobot Palynol 65:131–144. Doyle JA 2000 Paleobotany, relationships, and geographic history of Winteraceae. Ann Mo Bot Gard 87:303–316. Doyle JA, CL Hotton, JV Ward 1990 Early Cretaceous tetrads, zonasulculate pollen, and Winteraceae. I. Taxonomy, morphology, and ultrastructure. Am J Bot 77:1544–1557. Dusén P 1908 Über die tertiare ﬂora der Seymour Insel. Pages 1–27 in O Nordenskjöld, ed. Wissenschaftliche ergebnisse der Schwedischen Südpolar–expedition 1901–1903, geologie und paläontologie. Norstedt & Söner, Stockholm. Feild TS, MA Zwieniecki, NH Holbrook 2000 Winteraceae evolution: an ecophysiological perspective. Ann Mo Bot Gard 87:323–334. Frenguelli J 1943 Proteáceas del Cenozoico de Patagonia. Notas Mus La Plata Bot 8:201–213. Gandolfo MA, EJ Hermsen 2017 Ceratopetalum (Cunoniaceae) fruits of Australasian afﬁnity from the early Eocene Laguna del Hunco ﬂora, Patagonia, Argentina. Ann Bot 119:507–516. Gandolfo MA, EJ Hermsen, MC Zamaloa, KC Nixon, CC González, P Wilf, NR Cúneo, KR Johnson 2011 Oldest known Eucalyptus macrofossils are from South America. PLoS ONE 6:e21084. Gosses J, AR Carroll, BT Bruck, BS Singer, BR Jicha, E Aragón, AR Walters, P Wilf 2020 Facies interpretation and geochronology of diverse Eocene ﬂoras and faunas, northwest Chubut Province, Patagonia, Argentina. GSA Bull, https://doi.org/10.1130/B35611.1. Gottwald H 1992 Hölzer aus marinen sanden des Oberen Eozän von Helmstedt (Niedersachsen). Palaeontogr B 225:27–103. Grímsson F, GW Grimm, AJ Potts, R Zetter 2018 A Winteraceae pollen tetrad from the early Paleocene of western Greenland, and the fossil record of Winteraceae in Laurasia and Gondwana. J Biogeogr 45:567–581. Grímsson F, A Xaﬁs, FH Neumann, R Zetter 2017 Pollen morphology of extant Winteraceae: a study allowing SEM-based afﬁliation of its fossil representatives. Acta Palaeobot 57:339–396. Hill RS 1994 History of the Australian vegetation: Cretaceous to recent. Cambridge University Press, Cambridge. IAWA (International Association of Wood Anatomists) Committee 1989 IAWA list of microscopic features for hardwood identiﬁcation. IAWA Bull, NS, 10:219–332. InsideWood 2004– InsideWood database. http://insidewood.lib.ncsu .edu/search. Kooyman RM, RJ Morley, DM Crayn, EM Joyce, M Rossetto, JWF Slik, JS Strijk, T Su, J-YS Yap, P Wilf 2019 Origins and assembly of Malesian rainforests. Annu Rev Ecol Evol Syst 50:119–143. Kooyman RM, P Wilf, VD Barreda, RJ Carpenter, GJ Jordan, JMK Sniderman, A Allen, et al 2014 Paleo-Antarctic rainforest into the modern Old World tropics: the rich past and threatened future of the “southern wet forest survivors.” Am J Bot 101:2121–2135. Liang XQ, P Lu, JW Zhang, T Su, ZK Zhou 2018 First fossils of Zygogynum from the Middle Miocene of central Yunnan, southwest China, and their palaeobiogeographic signiﬁcance. Palaeoworld 27:399–409. Lindley J 1836 Natural system of botany. 2nd ed. Longmann, Rees, Orme, Brown, Green & Longman, London. Marquínez X, LG Lohmann, LF Salatino, A Salatino, F González 2009 Generic relationships and dating of lineages in Winteraceae based on nuclear (ITS) and plastid (rpS16 and psbA-trnH) sequence data. Mol Phylogenet Evol 53:435–449. Massoni J, TLP Couvreur, H Sauquet 2015a Five major shifts of diversiﬁcation through the long evolutionary history of Magnoliidae (angiosperms). BMC Evol Biol 15:49. https://doi.org/10.1186 /s12862-015-0320-6. Massoni J, J Doyle, H Sauquet 2015b Fossil calibration of Magnoliidae, an ancient lineage of angiosperms. Palaeontol Electron 18.1. 2FC. http://palaeo-electronica.org/content/fc-2. Massoni J, F Forest, H Sauquet 2014 Increased sampling of both genes and taxa improves resolution of phylogenetic relationships within Magnoliidae, a large and early-diverging clade of angiosperms. Mol Phylogenet Evol 70:84–93. Metcalfe CR, L Chalk 1950 Anatomy of the dicotyledons. Vols 1 and 2. Clarendon, Oxford. Müller S, K Salomo, J Salazar, J Naumann, MA Jaramillo, C Neinhuis, TS Feild, S Wanke 2015 Intercontinental long-distance dispersal of Canellaceae from the New to the Old World revealed by a nuclear single copy gene and chloroplast loci. Mol Phylogenet Evol 84:205– 219. Olivero EB 2012 Sedimentary cycles, ammonite diversity and palaeoenvironmental changes in the Upper Cretaceous Marambio Group, Antarctica. Cretac Res 34:348–366. Olivero EB, V Barreda, SA Marenssi, SN Santillana, DR Martinioni 1998 Estratigraﬁa, sedimentologia y palinologia de la Formación Sloggett (Paleogeno continental), Tierra del Fuego. Rev Asoc Geol Argent 53:504–516. Page VM 1979 Dicotyledonous wood from the Upper Cretaceous of central California. J Arnold Arbor 60:323–349. ——— 1981 Dicotyledonous wood from the Upper Cretaceous of central California. III. Conclusions. J Arnold Arbor 62:437–455. Patel RN 1974 Wood anatomy of the dicotyledons indigenous to New Zealand. IV. Winteraceae. N Z J Bot 12:19–32. Petersen CS 1946 Estudios geológicos en la región del Río Chubut medio. Secretaría de Industria y Comercio, Buenos Aires. Pipo ML, A Iglesias, J Bodnar 2020 A new vesselless angiosperm stem with a cambial variant from the Upper Cretaceous of Antarctica. Acta Palaeontol Pol 65:261–272. Poole I, JE Francis 2000 The ﬁrst record of fossil wood of Winteraceae from the Upper Cretaceous of Antarctica. Ann Bot 85:307–315. Pujana RR, P Wilf, MA Gandolfo 2020 Conifer wood assemblage dominated by Podocarpaceae, early Eocene of Laguna del Hunco, central Argentinean Patagonia. Phytokeys 156:81–102. Qiu Y-L, O Dombrovska, J Lee, L Li, BA Whitlock, F BernasconiQuadroni, JS Rest, et al 2005 Phylogenetic analyses of basal angiosperms based on nine plastid, mitochondrial, and nuclear genes. Int J Plant Sci 166:815–842. BREA ET AL.—FIRST SOUTH AMERICAN RECORD OF WINTEROXYLON Qiu Y-L, J Lee, F Bernasconi-Quadroni, DE Soltis, PS Soltis, M Zanis, EA Zimmer, Z Chen, V Savolainen, MW Chase 1999 The earliest angiosperms: evidence from mitochondrial, plastid and nuclear genomes. Nature 402:404–407. Rancusi MH, M Nishida, H Nishida 1987 Xylotomy of important Chilean woods. Pages 68–153 in M Nishida, ed. Contributions to the botany in the Andes. Vol 2. Academic Scientiﬁc Book, Tokyo. Richter HG, MJ Dallwitz 2000 Commercial timbers: descriptions, illustrations, identiﬁcation, and information retrieval. http://www.delta -intkey.com/wood/index.htm. Romero EJ, MC Dibbern, MA Gandolfo 1988 Revisión de Lomatia bivascularis (Berry) Frenguelli (Proteaceae) del yacimiento de la Laguna del Hunco (Paleoceno), Pcia. del Chubut. Pages 125–130 in Actas del IV Congreso Argentino de Paleontología y Bioestratigrafía, Mendoza. Rossetto-Harris G, P Wilf, IH Escapa, A Andruchow-Colombo 2020 Eocene Araucaria sect. Eutacta from Patagonia and ﬂoristic turnover during the initial isolation of South America. Am J Bot 107:806–832. Schrank E 2013 New taxa of winteraceous pollen from the Lower Cretaceous of Israel. Rev Palaeobot Palynol 195:19–25. Schweingruber FH, A Börner, ED Schulze 2011 Atlas of stem anatomy in herbs, shrubs and trees. Vol 1. Springer, Berlin. Scott RA, EA Wheeler 1982 Fossil woods from the Eocene Clarno Formation of Oregon. IAWA Bull, NS, 3:135–154. Soltis PS, DE Soltis 2004 The origin and diversiﬁcation of angiosperms. Am J Bot 91:1614–1626. Suh Y, LB Thien, HE Reeve, EA Zimmer 1993 Molecular evolution and phylogenetic implications of internal transcribed spacer sequences of ribosomal DNA in Winteraceae. Am J Bot 80:1042–1055. Suzuki M, L Joshi, T Fujii, S Noshiro 1991 The anatomy of unusual tracheids in Tetracentron wood. IAWA Bull, NS, 12:23–33. Swamy BGL, IW Bailey 1950 Sarcandra, a vesselless genus of the Chloranthaceae. J Arnold Arbor 31:117–129. Thomas N, JJ Bruhl, A Ford, PH Weston 2014 Molecular dating of Winteraceae reveals a complex biogeographical history involving both ancient Gondwanan vicariance and long-distance dispersal. J Biogeogr 41:894–904. Tortorelli LA 1956 Maderas y bosques Argentinos. Editorial Acme, Buenos Aires. 000 Tosolini AM, DJ Cantrill, JE Francis 2013 Paleocene ﬂora from Seymour Island, Antarctica: revision of Dusén’s (1908) angiosperm taxa. Alcheringa 37:366–391. Vink W 1985 The Winteraceae of the Old World. V. Exospermum links Bubbia to Zygogynum. Blumea 31:39–55. ——— 1988 Taxonomy in Winteraceae. Taxon 37:691–698. ——— 1993 Winteraceae. Pages 630–638 in K Kubitzki, JG Rohwer, V Bittich, eds. The families and genera of vascular plants: ﬂowering plants: dicotyledons. Vol 2. Springer, Berlin. Walker JW, GJ Brenner, AG Walker 1983 Winteraceous pollen in the Lower Cretaceous of Israel: early evidence of a magnolialean angiosperm family. Science 220:1273–1275. Wheeler EA 2011 InsideWood: a web resource for hardwood anatomy. IAWA J 32:199–211. Wilf P 2012 Rainforest conifers of Eocene Patagonia: attached cones and foliage of the extant Southeast Asian and Australasian genus Dacrycarpus (Podocarpaceae). Am J Bot 99:562–584. Wilf P, NR Cúneo, IH Escapa, D Pol, MO Woodburne 2013 Splendid and seldom isolated: the paleobiogeography of Patagonia. Annu Rev Earth Planet Sci 41:561–603. Wilf P, NR Cúneo, KR Johnson, JF Hicks, SL Wing, JD Obradovich 2003 High plant diversity in Eocene South America: evidence from Patagonia. Science 300:122–125. Wilf P, KR Johnson, NR Cúneo, ME Smith, BS Singer, MA Gandolfo 2005 Eocene plant diversity at Laguna del Hunco and Río Pichileufú, Patagonia, Argentina. Am Nat 165:634–650. Wilf P, SA Little, A Iglesias, MC Zamaloa, MA Gandolfo, NR Cúneo, KR Johnson 2009 Papuacedrus (Cupressaceae) in Eocene Patagonia: a new fossil link to Australasian rainforests. Am J Bot 96:2031– 2047. Wilf P, KC Nixon, MA Gandolfo, NR Cúneo 2019 Eocene Fagaceae from Patagonia and Gondwanan legacy in Asian rainforests. Science 364:eaaw5139. https://doi.org/10.1126/science.aaw5139. Zamaloa MC, MA Gandolfo, CC González, EJ Romero, NR Cúneo, P Wilf 2006 Casuarinaceae from the Eocene of Patagonia, Argentina. Int J Plant Sci 167:1279–1289. Zanis MJ, PS Soltis, Y-L Qiu, EA Zimmer, DE Soltis 2003 Phylogenetic analyses and perianth evolution in basal angiosperms. Ann Mo Bot Gard 90:129–150.

RELATED PAPERS

RELATED TOPICS

Log In

FIRST SOUTH AMERICAN AGATHIS (ARAUCARIACEAE), EOCENE OF PATAGONIA

FIRST SOUTH AMERICAN AGATHIS (ARAUCARIACEAE), EOCENE OF PATAGONIA

Related Papers

RELATED PAPERS

RELATED TOPICS