Panciroli, Elsa, Walsh, Stig A, Fraser, Nicholas C, Brusatte, Stephen L and Corfe, Ian (2017) A reassessment of the postcanine dentition and systematics of the tritylodontid Stereognathus (Cynodontia, Triltylodontidae, Mammaliamorpha) from the Middle Jurassic of the United Kingdom. Journal of Vertebrate Paleontology, 37 (5). ISSN 1937-2809

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Abstract

Tritylodontidae was a successful advanced cynodont clade with a close relationship to mammals, but falling outside the clade Mammaliaformes. Stereognathus ooliticus was the first tritylodontid to be named and described in 1854, but since then no comprehensive description for this species has been produced. A second species, S. hebridicus, was named in 1972 and diagnosed based solely on size difference, being larger than the S. ooliticus holotype. We reexamined all postcanine tooth material attributed to the genus Stereognathus to test the species diagnosis and identify diagnostic morphological characters for this genus. We find no statistical difference in size distribution between S. ooliticus and S. hebridicus postcanine specimens. Specimens previously attributed to the different species fall along an ontogenetic spectrum of size, with no clear clustering. Morphologically, we affirm many previously described features for Stereognathus and identify new morphological features in upper and lower postcanines. We find no morphological features to distinguish these two species, and therefore we synonymize S. hebridicus under S. ooliticus. We reevaluate the scoring of S. ooliticus in previous phylogenetic analyses, generating a new tree using rescored Stereognathus characters. Finally, we suggest that similar reevaluations and redescriptions of other poorly described tritylodontid material are necessary to further clarify relationships among Tritylodontidae and the evolution of characters in derived genera such as Stereognathus.

Item Type: Article
Subjects: D History General and Old World > DA Great Britain
G Geography. Anthropology. Recreation > GE Environmental Sciences
Q Science > QD Chemistry
Q Science > QE Geology
Q Science > QH Natural history
Q Science > QL Zoology
Theme: Understanding the natural world
Department: Natural Sciences
Related URLs:
Depositing User: Ross Anderson
Date Deposited: 29 Nov 2017 12:05
Last Modified: 29 Nov 2017 12:05
URI: http://repository.nms.ac.uk/id/eprint/1948

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