Abstract
Herein we describe a new rhynchocephalian taxon from the Middle Jurassic of Patagonia, Argentina, representing the first Jurassic record of the group in South America. The new taxon, consisting of a complete dentary, is ascribed to Sphenodontia based on the presence of a deep and wide Meckelian groove, long posterior process, well-developed coronoid process, and acrodont teeth showing dental regionalization including successional, alternate hatchling, and additional series. This allocation is reinforced by a phylogenetic analysis that places the new taxon in a basal position within a clade of sphenodontians that excludes Diphydontosaurus and Planocephalosaurus. Additionally, the new taxon clusters within a Gondwanan clade with the Indian Godavarisaurus from the Jurassic Kota Formation, sharing the presence of recurved and relatively large posterior successional teeth that are ribbed and bear a peculiar anterolingual groove. This sister-group relationship is intriguing from a palaeobiogeographical viewpoint, as it suggests some degree of endemism during the initial stages of the breakup of Pangaea. We also discuss the ontogenetic stage of the new taxon and provide insights on the evolution of successional dentition in rhynchocephalians. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166, 342–360.
Highlights
Rhynchocephalia (Günther, 1867 sensu Gauthier, Estes & De Queiroz, 1988) is a clade of lizard-like reptiles that, together with Squamata, constitute the Lepidosauria (Carroll, 1977; Evans, 1984; Benton, 1985; Gauthier et al, 1988)
The affinities of Homoeosaurus to other sphenodontians are still poorly understood, despite the analysis developed by Wu (1994); its nested position within eupropalinal sphenodontians is in conflict with previous hypotheses in that it takes a more basal position within derived sphenodontians (e.g. Reynoso, 1996; Apesteguía & Novas, 2003)
Sphenocondor represents a key taxon for understanding the evolution of rhynchocephalians in southern continents, breaking a vast gap in the South American record that extended from the Upper Triassic to the Lower Cretaceous
Summary
Rhynchocephalia (Günther, 1867 sensu Gauthier, Estes & De Queiroz, 1988) is a clade of lizard-like reptiles that, together with Squamata, constitute the Lepidosauria (Carroll, 1977; Evans, 1984; Benton, 1985; Gauthier et al, 1988). Southern Triassic records include fragmentary material from Africa (Gow & Raath, 1977; Sues & Reisz, 1995) and well-preserved clevosaurs from Brazil Clark et al, 1994; Reynoso, 1996, 1997, 2005), and China (Evans, 1992), whereas southern regions only include fragmentary remains from Zimbabwe (Gow & Raath, 1977), South Africa (Sues & Reisz, 1995), and India (Evans, Prasad & Manhas, 2001). The Middle and Late Jurassic record of the group was, up to now, restricted to the Northern Hemisphere, with no records from Gondwanan landmasses This Laurasian record includes fragmentary material from the UK (Evans, 1992), France The South American record of rhynchocephalians exhibits a time gap of more than 100 million years, from the Late Triassic (Norian) of Brazil (Caturrita Formation; Ferigolo, 1999) to the early Late Cretaceous (Cenomanian) of Patagonia (Candeleros Formation; Apesteguía & Novas, 2003)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
