Earth-Science Reviews 210 (2020) 103331 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev Invited Review Early Triassic terrestrial tetrapod fauna: a review T ⁎ Marco Romanoa,b, Massimo Bernardic,d, , Fabio Massimo Pettic, Bruce Rubidgeb, John Hancoxb, Michael J. Bentond a Dipartimento di Scienze della Terra, Sapienza Università di Roma, P.le A. Moro 5, 00185 Rome, Italy b Evolutionary Studies Institute (ESI) and School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa c MUSE – Museo delle Scienze, Corso del Lavoro e della Scienza 3, 38122 Trento, Italy d School of Earth Sciences, University of Bristol, Queens Road, Bristol BS8 1RJ, UK ARTICLE INFO ABSTRACT Keywords: The Permian-Triassic mass extinction (PTME, ca. 252 Mya) was one of the most severe biotic crises of the Tetrapods Phanerozoic, eliminating > 90% of marine and terrestrial species. This was followed by a long period of re- Early Triassic covery in the Early and Middle Triassic which revolutionised the structure of both marine and terrestrial eco- Late Permian systems, triggering the new ecosystem structure of the Mesozoic and Cenozoic. Entire new clades emerged after Permo-Triassic mass extinction the mass extinction, including decapods and marine reptiles in the oceans and new tetrapods on land. In both marine and terrestrial ecosystems, the recovery is interpreted as stepwise and slow, from a combination of continuing environmental perturbations and complex multilevel interaction between species in the new en- vironments as ecosystems reconstructed themselves. Here, we present a review of Early Triassic terrestrial tet- rapod faunas, geological formations and outcrops around the world, and provide a semi-quantitative analysis of a data set of Early Triassic terrestrial tetrapods. We identify a marked regionalisation of Early Triassic terrestrial tetrapods, with faunas varying in both taxonomic composition and relative abundance according to palaeola- titudinal belt. We reject the alleged uniformity of faunas around Pangaea suggested in the literature as a result of the hot-house climate. In addition, we can restrict the “tetrapod gap” of terrestrial life in the Early Triassic to palaeolatitudes between 15°N and about 31°S, in contrast to the earlier suggestion of total absence of tetrapod taxa between 30°N and 40°S. There was fairly strong provincialism following the PTME, according to cluster analysis of a taxon presence matrix, entirely consistent with Early Triassic palaeobiogeography. Unexpectedly, the overall pattern for Early Triassic terrestrial tetrapod faunas largely reflects that of the Late Permian, sug- gesting that the recovery faunas in the Early Triassic retained some kind of imprint of tetrapod distributions according to palaeogeography and palaeoclimate, despite the near-total extinction of life through the PTME. 1. Introduction revolutionised the structure of both marine and terrestrial ecosystems (Chen and Benton, 2012), influencing the course of evolution in the The mass extinction at the Permian–Triassic boundary (PTB; ca. 252 remainder of the Mesozoic and Cenozoic eras (Sepkoski, 1984; Benton, Mya) eliminated > 90% of marine and terrestrial species (Erwin, 1993; 2010). Entire new groups emerged after the crisis, including new tet- Song et al., 2013, 2015; see Stanley, 2016 for a slightly lower estimate) rapods on land and decapods and marine reptiles in the oceans (Chen and is widely considered the most severe biotic crisis in Earth's history and Benton, 2012). Several lineages of sauropsids diversified rapidly (Sepkoski, 1984; Raup and Sepkoski, 1982; Sheldon and Retallack, during the 5 Myr of the Early Triassic both on land (Butler et al., 2011; 2002; Benton and Twitchett, 2003; Smith and Botha-Brink, 2014; Ward Nesbitt et al., 2010a; Gower et al., 2014) and in the sea (Scheyer et al., et al., 2005; Lehrmann et al., 2006; Knoll et al., 2007; Isozaki et al., 2014; Motani et al., 2015a, 2015b). Cynodonts and archosaurs came to 2007; Roopnarine et al., 2007, 2018; Sahney and Benton, 2008; Lucas, prominence during the Triassic recovery and, among archosaurs, ave- 2009; Metcalfe and Isozaki, 2009; Korte et al., 2010; Chen and Benton, metatarsalians (the lineage including dinosaurs and pterosaurs) origi- 2012; Hermann et al., 2011; Song et al., 2011; Chen et al., 2015; nated during this time (Brusatte et al., 2010; Nesbitt et al., 2010b, 2017; Roopnarine and Angielczyk, 2015; Song et al., 2018; Dineen et al., Chen and Benton, 2012; Benton et al., 2014). 2019). The long period of recovery in the Early and Middle Triassic Taking into consideration the great importance of the Early Triassic ⁎ Corresponding author at: MUSE – Museo delle Scienze, Corso del Lavoro e della Scienza 3, 38122 Trento, Italy. E-mail address: [email protected] (M. Bernardi). https://doi.org/10.1016/j.earscirev.2020.103331 Received 27 March 2020; Received in revised form 19 August 2020; Accepted 24 August 2020 Available online 31 August 2020 0012-8252/ Crown Copyright © 2020 Published by Elsevier B.V. All rights reserved. M. Romano, et al. Earth-Science Reviews 210 (2020) 103331 for the re-structuring of ecosystems after the Permo-Triassic mass ex- clathrate reservoirs (see Berner, 2002). In turn, this led to global tinction (PTME), and following the approaches adopted by Bernardi warming and to the production of acid rain that caused plant die-offs et al. (2017) in their analysis of the Late Permian, in this contribution and associated intensive soil erosion (see Wignall, 2001; Benton, 2003, we provide a review of terrestrial vertebrate faunas around the world at 2018; Benton and Twitchett, 2003; Sephton et al., 2005; Knoll et al., the beginning of the Mesozoic Era. Early Triassic tetrapod assemblages, 2007). Studies conducted on conodont bioapatite stable oxygen iso- known from both body fossils and footprints, have been reported from topes (Joachimski et al., 2012; Sun et al., 2012) highlight an increase in Antarctica, Argentina, Australia, Brazil, Canada, China, England, Ger- sea surface temperature of about ~9 °C from Bed 24e to Bed 27a in the many, Greenland, India, Italy, Japan, Kenya, Laos, Mongolia, Morocco, Meishan section (South China). The global warming, starting at the Madagascar, Niger, Pakistan, Poland, Russia, Scotland, Spain, the extinction horizon and continuing into the Early Triassic (Joachimski United States and South Africa (see detailed references below). For the et al., 2012; Sun et al., 2012; Schobben et al., 2014; Song et al., 2015), present analysis, 11 geographic regions were selected on the basis of probably also triggered the release of methane from coals and deep geological domains and palaeolatitudes and a comprehensive dataset ocean sediments, with additional greenhouse gases released by inter- has been generated to provide a semi-quantitative analysis of faunal actions between the Siberian traps and local limestones, permafrost composition in the Early Triassic. For each region, a short review is soils, and other organic-rich sediments (Krull et al., 2000; Dorritie, provided of the geology and fossiliferous formations and outcrops, 2002; Racki, 2003; Racki and Wignall, 2005; Retallack and Jahren, along with the percentage occurrences for the principal clades. 2008; Grasby et al., 2011). Konstantinov et al. (2014) stress how the Siberian LIP was underlain by a really thick succession of Permian- and 2. Causes of the PTME and its effects on the marine realm Carboniferous-aged carbonates, coal-bearing deposits and evaporites, which could produce large volume of poisonous and greenhouse gases 2.1. Siberian Traps eruptions and their consequences (see Svensen et al., 2009; Ganino and Arndt, 2009), and they hy- pothesize a great influence of huge and fast injections of magma into Over the last three decades several hypotheses have been proposed such underlying sediments as the key driver of the Permo-Triassic crisis. to explain the PTME, including the eruption of the Siberian Traps and Together, it is estimated that 30,000 to 40,000 Gt of carbon were re- Emeishan Traps (Campbell et al., 1992; Renne et al., 1995; Bowring leased (Clarkson et al., 2015), potentially overwhelming climate-reg- et al., 1998; Chung et al., 1998; Courtillot, 1999; Jin et al., 2000; ulating mechanisms of the time and causing positive feedback that Wignall, 2001; Lo et al., 2002; Kamo et al., 2003; Racki and Wignall, exacerbated ocean anoxia, increased global warming, and sustained 2005; Reichow et al., 2009; Saunders and Reichow, 2009; Grasby et al., ocean acidification (see Wignall, 2001; Chen and Benton, 2012; 2011; Konstantinov et al., 2014; Shen et al., 2019), and a bolide impact Clarkson et al., 2015; Kump, 2018). In the marine realm, Song et al. (Kaiho et al., 2001; Becker et al., 2001, 2004; Basu et al., 2003). (2014) propose a model where the spectrum of extinction selectivity is However, the evidence for a bolid impact has been criticized (Isozaki, explained by a combination of lethally warm shallow waters and anoxic 2001; Erwin, 2003; Koeberl et al., 2002, 2004; Farley et al., 2005; Xie deep waters, which led to a consistent restriction of habitable area to a et al., 2007) and considered both unnecessary and inadequate to ex- narrow mid-water refuge zone. According to these authors, shallow plain the biotic crisis (Ward et al., 2005; Tohver et al., 2012, 2013, water organisms like corals, large foraminifers and radiolarians intol- 2018). In this regard, Ward