Paleobiology, 46(4), 2020, pp. 445–469 DOI: 10.1017/pab.2020.45 Featured 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 heteroge- neous 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-con- strained 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 esti- mated across the K/Pg, consistent with substantial species-level extinction and previously observed extir- pation 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 com- pared 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 spe- cies 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 macro- floras 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: [email protected].*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: [email protected] 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: [email protected] 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: [email protected] N. Rubén Cúneo. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)–Museo Paleontológico Egidio Feruglio, Avenida Fontana 140, Trelew 9100, Chubut, Argentina. E-mail: [email protected] Accepted: 27 August 2020 Data available from the Dryad Digital Repository: https://doi.org/10.5061/dryad.jsxksn071 Introduction et al. 2010). Although the K/Pg event affected The devastating environmental conse- biotas globally, the severity of the extinction quences of the end-Cretaceous bolide impact and the pacing of the recovery were geograph- affected both marine and terrestrial organisms ically heterogeneous for some groups of organ- (e.g., Alvarez et al. 1980; Prinn and Fegley isms (see next paragraph). Modern biodiversity 1987; Robertson et al. 2013; Vellekoop et al. is shaped by the surviving lineages of the K/Pg 2014; Tyrrell et al. 2015; Artemieva and Morgan (e.g., Erwin 2002; Krug et al. 2017), establishing 2017; Brugger et al. 2017). Over 60% of Cret- today’s biogeographic patterns, in part, as the aceous species became extinct, making the legacy of a globally heterogeneous extinction Cretaceous–Paleogene (K/Pg) event the most (e.g., Wolfe 1987). recent of the “big five” mass extinctions (Raup Southern Hemisphere records of calcareous and Sepkoski 1982; Jablonski 2005; Schulte nannoplankton, insect herbivory, and terrestrial © The Author(s), 2020. Published by Cambridge University Press on behalf of The Paleontological Society. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/ Downloadedlicenses/by/4.0/ from https://www.cambridge.org/core), which permits unrestricted. IP address: 170.106.35.93 re-use, distribution,, on 25 Sep 2021 and at reproduction 19:50:38, subject in to any the medium, Cambridge provided Core terms the of original use, availablework at ishttps://www.cambridge.org/core/terms properly cited. https://doi.org/10.1017/pab.2020.45 0094-8373/20 446 ELENA STILES ET AL. palynomorphs indicate lower extinction and/ Zealand revealed a dramatic floral turnover or faster recoveries than Northern Hemisphere (Pole and Vajda 2009) and a paleoclimatic cool- counterparts (Vajda et al. 2001; Vajda and ing trend consistent with global records (Ken- Raine 2003; Iglesias et al. 2007; Pole and Vajda nedy et al. 2002) across the K/Pg, but the 2009; Jiang et al. 2010; Barreda et al. 2012; Can- severity of the macrofloral extinction was not trill and Poole 2012; Schueth et al. 2015; Dono- estimated. Until now, no well-constrained and van et al. 2016). Furthermore, several plant and well-sampled macrofloral Maastrichtian and vertebrate groups that had been known only Danian sites from the same region have been from Mesozoic localities in the Northern Hemi- available in the Southern Hemisphere. sphere, have been reported in Cenozoic South- Recent studies of the latest Cretaceous (Maas- ern Hemisphere deposits suggesting that they trichtian) Lefipán and early Paleocene (Danian) survived the K/Pg in southern latitudes (Case Salamanca and Peñas Coloradas Formations of and Woodburne 1986; Pascual et al. 1992; Bona- Chubut, Argentine Patagonia (Fig. 1; and see parte et al. 1993; Goin et al. 2006, 2012; “Materials” and “Analytical Methods”) showed McLoughlin et al. 2008, 2011; Gelfo et al. lower palynological extinction, faster recovery 2009; Sterli and de la Fuente 2019). Proposed of insect herbivory damage-type diversity, and explanations for this geographic heterogeneity remarkably diverse Danian macrofloras com- (Jiang et al. 2010; Donovan et al. 2016, 2018) pared with most NAM sections of the same have referenced increased distance from the ages. Specifically, spore and pollen records Mexican impact site (Schulte et al. 2010), showed <10% extinction across the K/Pg com- oceanic buffering of impact winter tempera- pared with the 30%–40% extinction in NAM tures in the Southern Hemisphere (Bardeen palynofloras (Nichols and Fleming 1990; et al. 2017; Tabor et al. 2020), and a bolide Sweet and Braman 2001; Hotton 2002; Nichols impact angle that would have directed most 2002; Barreda et al. 2012). Notably, in early ejecta and debris northward (Schultz and Danian Patagonian pollen records, an abun- D’Hondt 1996). dance spike of the conifer Classopollis represents Because plants are the primary producers in the last record of a genus that is otherwise only terrestrial ecosystems and one of the most bio- known until the Late Cretaceous worldwide diverse groups of organisms, the paleobotan- (Barreda et al. 2012). Insect feeding-damage ical record is critical for understanding types on angiosperm leaves recovered to extinction events on land (e.g., Nichols and pre-K/Pg diversity levels within about 4 Myr, Johnson 2008). However, the vast majority of compared with the estimated ca. 9 Myr for plant-bearing K/Pg continental sites is concen- NAM (Donovan et al. 2016, 2018), and Danian trated in the western interior of North America macrofloras of the Salamanca Formation are (NAM), which bears numerous examples of much more diverse than most coeval NAM stratigraphically and temporally well con- counterparts, suggesting a faster-paced Patago- strained boundary-spanning palynofloras nian recovery (Iglesias et al. 2007). However, (e.g., Nichols et al. 1986; Nichols and Fleming comparable Maastrichtian leaf floras from the 1990; Sweet et al. 1990, 1999; Sweet and Braman same Patagonian region have not yet been eval- 2001; Nichols 2002; Bercovici et al. 2009) and uated using similar methods. macrofloras (e.g., Wolfe and Upchurch 1986; Gymnosperm macrofossils of the Lefipán Johnson et al. 1989; Johnson and Hickey 1990; and Salamanca Formations have been the sub- Johnson 1992, 2002; Upchurch 1995; Barclay ject of taxonomic studies (Zamuner et al. et al. 2003; Nichols and Johnson 2008). South- 2000; Brea et al. 2005; Quiroga et al. 2015; ern Hemisphere K/Pg-spanning paleofloras Ruiz et al. 2017; Wilf et al. 2017; Andruchow- are scarce and have been primarily limited to Colombo et al. 2018, 2019; Escapa et al. 2018), palynological records (e.g., Vajda-Santivanez indicating the survival of the Podocarpaceae 1999; Vajda et al. 2001; Vajda and Raine 2003; and Araucariaceae conifer families. The pres- Pole and Vajda 2009; Barreda et al. 2012; Can- ence of several derived angiosperm groups trill and Poole 2012; Scasso et al. 2020). Cret- known from reproductive material in the Sala- aceous–Paleogene macrofloras from New manca Formation suggests that they also Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.93, on 25 Sep 2021 at 19:50:38, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms.