A new clevosaurid (Lepidosauria: Rhynchocephalia) from the Upper Triassic of India

ABSTRACT

A new clevosaurid rhynchocephalian is described from the Upper Triassic Tiki Formation of the Rewa Gondwana Basin of India. The material is based on several partial craniomandibular elements containing acrodont and fully ankylosed tooth implantations and on the basis of multiple diagnostic features is assigned to a new taxon, Clevosaurus nicholasi. Phylogenetic analysis nests the Tiki rhynchocephalian within the clade Clevosauridae, where it is recovered as an early-diverging taxon basal to the other clevosaurs except for a clade comprising C. convallis + Sigmala sigmala. The autapomorphic characters of Clevosaurus nicholasi include a very robust dentary with an obliquely angled narrow lip of the secondary bone at the symphysis, anteriorly bifurcated Meckelian canal, a sub-dental shelf on the dentary, acrodont marginal anterior teeth, and absence of or smooth lateral and medial wear facets on the marginal dentary and maxillary teeth, respectively. The Late Triassic rhynchocephalian record of the Gondwana is relatively sparse in comparison with that of the Laurasian regions, and the new clevosaur represents the first Late Triassic record from India. Based on the paleobiogeographic distribution, a possible Gondwanan origin for Clevosauridae is hypothesized.

ACKNOWLEDGMENTS

We are grateful to D. Mukherjee (Geological Studies Unit, Indian Statistical Institute, Kolkata, India) and N. Rakshit (Department of Earth Sciences, Indian Institute of Technology, Bombay, Mumbai, India) for active participation in the field during the fossil excavation. We acknowledge A. Bhaumik (Department of Applied Geology, Indian School of Mines, Dhanbad, India) and N. Bhowmik (Central Research Facility, Indian Institute of Technology, Kharagpur, India) for facilitating scanning electron microscopy. The constructive comments and helpful suggestions by G. Bever (Editor), P. L. Godoy (Phylogenetics Editor), M. E. H. Jones and two anonymous reviewers are gratefully acknowledged. The software TNT is freely available courtesy of the Willi Hennig Society. Financial assistance and infrastructural facilities were provided by the Department of Science and Technology, India (SERB/SR/S4/ES-604/2012) and the Indian Institute of Technology, Kharagpur, India, respectively.

LIST OF SUPPLEMENTARY FILES

Supplementary Data 1.docx: Character matrix of Clevosaurus nicholasi used for phylogenetic analysis.

Supplementary Data 2.nex: character-taxon matrix.

Additional information

Notes on contributors

Mohd Shafi Bhat

MSB: conceptualization, data curation, formal analysis, investigation, methodology, software, validation, visualization, writing original draft, writing—review and editing

Debajit Datta

DD: investigation, software, validation, visualization, writing original draft, writing—review and editing.

Sanghamitra Ray

SR: conceptualization, data curation, project administration, funding acquisition, resources, software, supervision, writing original draft, writing—review and editing

P. M. Datta

PMD: methodology, supervision, writing—review and editing.