Journal of Paleontology, 92(4), 2018, p. 734–742 Copyright © 2018, The Paleontological Society. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (
http://creativecommons.org/ licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. 0022-3360/18/0088-0906 doi: 10.1017/jpa.2017.136
Taxonomic reassessment of Clevosaurus latidens Fraser, 1993 (Lepidosauria, Rhynchocephalia) and rhynchocephalian phylogeny based on parsimony and Bayesian inference
Jorge A. Herrera-Flores, Thomas L. Stubbs, Armin Elsler, and Michael J. Benton
School of Earth Sciences, University of Bristol, Queens Road, Bristol BS8 1RJ, UK ⟨
jorge.herreraflores@bristol.ac.uk⟩⟨
tom.stubbs@
bristol.ac.uk⟩ ⟨
armin.elsler@bristol.ac.uk⟩⟨
mike.benton@
bristol.ac.uk⟩
Abstract.—The Late Triassic rhynchocephalian Clevosaurus latidens Fraser, 1993 is known from the fissure deposits of Cromhall Quarry, England. Many studies have questioned its referral to the genus Clevosaurus Swinton, 1939 and some phylogenetic analyses suggest a close relationship with herbivorous rhynchocephalians. We re-examine the type specimens and referred material of C. latidens to elucidate its taxonomic identity. Additionally, we provide new phylogenetic analyses of the Rhynchocephalia using both parsimony and Bayesian approaches. Our taxonomic review and both phylogenetic analyses reveal that C. latidens is not referable to Clevosaurus, but represents a new genus. We reassess C. latidens and provide an amended diagnosis for Fraserosphenodon new genus. Both parsimony and Bayesian analyses recover similar topologies and we propose formal names for two higher clades within Rhynch- ocephalia: Eusphenodontia new infraorder and Neosphenodontia new clade.
UUID:
http://zoobank.org/65f29bd1-47e3-4a73-af8c-9181c19319e4 Introduction
The Rhynchocephalia is an ancient group of reptiles that originated in the early Mesozoic. Currently this group has low diversity, being represented by a single species, the famous ‘living fossil’ Sphenodon punctatus (Gray, 1842) from New Zealand (Jones et al., 2013; Cree, 2014; Herrera-Flores et al., 2017). In contrast to their current low diversity, Mesozoic rhynchocepha- lians were diverse, showing varied morphologies and a wide geographical distribution (Jones, 2006a, 2009; Rauhut et al., 2012; Martínez et al., 2013; Herrera-Flores et al., 2017). Among the earliest rhynchocephalians, species of the genus Clevosaurus Swinton, 1939 were the most diverse and widely distributed in the early Mesozoic. Clevosaurus hudsoni Swinton, 1939 was the first described species of the genus; it was named after F. G. Hudson, who discovered the fossil remains at Cromhall Quarry, England (Fraser, 1988). Since the description of C. hudsoni, nine species of Clevosaurus have been erected—C. bairdi Sues, Shubin, and Olsen, 1994, C. brasiliensis Bonaparte and Sues, 2006, C. con- vallis Säilä, 2005, C. latidens Fraser, 1993, C. mcgilli Wu, 1994, C. minor Fraser, 1988, C. petilus Young, 1982, C. sectumsemper Klein et al., 2015, and C. wangi Wu, 1994—and new records have been reported from localities in Belgium, Brazil, Canada, China, Great Britain, Mexico, and South Africa (Fraser, 1988, 1993; Wu, 1994; Sues et al., 1994; Duffin, 1995; Sues and Reisz, 1995; Säilä, 2005; Bonaparte and Sues, 2006; Reynoso and Cruz, 2014; Klein et al., 2015). The anatomy of Clevosaurus is well known and the
monograph of Fraser (1988) offers a very thorough review of the general morphology of this genus. It is recognized that the
genus Clevosaurus is highly diverse, but the taxonomic validity of some Clevosaurus species has been questioned (Jones, 2006a). Hsiou et al. (2015) presented a review of C. brasiliensis that included a phylogenetic analysis of almost all known Clevosaurus species. Their study demonstrated that some spe- cies might not be valid taxa or are perhaps not directly referable to this genus. One of these conflicting taxa is C. latidens,a species described by Fraser (1993) from the Late Triassic fissure deposits of Cromhall Quarry, England. The uncertain taxo- nomic affinity of C. latidens and its dubious relationship with Clevosaurus have been noted in many previous studies (Jones, 2006a, 2009; Martínez et al., 2013; Hsiou et al., 2015; Klein et al., 2015), and some phylogenetic analyses even suggested a closer relationship with opisthodontians, but no taxonomic revision of this taxon has been carried out. For a long time, the relationships among rhynchocepha-
lians were poorly known, and most taxa were assessed by overall morphological similarities. The first phylogenetic ana- lysis of the group was performed by Fraser and Benton (1989), followed by many different analyses, including new descrip- tions or redescriptions of taxa (e.g., Wu, 1994; Reynoso, 1996, 1997, 2000, 2005; Reynoso and Clark, 1998; Apesteguía and Novas, 2003; Rauhut et al., 2012; Martínez et al., 2013; Apesteguía and Carballido, 2014; Apesteguía et al., 2012, 2014; Cau et al., 2014; Hsiou et al., 2015). So far, all phylogenetic studies of the Rhynchocephalia have only used parsimony analysis, recovering a fewdistinct clades. More recently, Bayesian inference methods have been employed for phylogenetic analyses based on morphological characters (e.g., Parry et al., 2016; Wright, 2017), and recent studies suggest that Bayesian
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