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Article: A new Hyperodapedon (Archosauromorpha, Rhynchosauria) from the Upper Triassic of India: implications for rhynchosaur phylogeny

Publication: Palaeontology
Volume: 57
Part: 6
Publication Date: November 2014
Page(s): 1241 1276
Author(s): Debarati Mukherjee and Sanghamitra Ray
Addition Information

How to Cite

MUKHERJEE, D., RAY, S. 2014. A new Hyperodapedon (Archosauromorpha, Rhynchosauria) from the Upper Triassic of India: implications for rhynchosaur phylogeny. Palaeontology, 57, 6, 1241-1276.

Author Information

  • Debarati Mukherjee - Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, West Bengal, India (email: mdebarati.iitkgp@gmail.com; mdebarati@isical.ac.in)
  • Debarati Mukherjee - Geological Studies Unit, Indian Statistical Institute, Kolkata, West Bengal, India
  • Sanghamitra Ray - Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, West Bengal, India (email: sray@gg.iitkgp.ernet.in)

Publication History

  • Issue published online: 25 NOV 2014
  • Article first published online: 15 MAY 2014
  • Manuscript Accepted: 17 MAR 2014
  • Manuscript Received: 5 JUL 2013

Funded By

Indian Institute of Technology, Kharagpur
Department of Science and Technology
Council of Scientific and Industrial Research, India

Online Version Hosted By

Wiley Online Library
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Abstract

A new species of the rhynchosaur genus Hyperodapedon, namely H. tikiensis, is described from well-preserved skeletal elements that were collected from the Upper Triassic Tiki Formation of India. Hyperodapedon tikiensis is diagnosed on the basis of several cranial and postcranial features including longer than wide basipterygoid process, crest-shaped maxillary cross section lateral to the main longitudinal groove, deeply excavated neural arches of mid-dorsal vertebrae, long scapular blade, a pronounced deltopectoral crest, proximal humeral end much broader than distal end, iliac length greater than iliac height, equal pre- and postacetabular iliac lengths and circular femoral cross section. Two distinct morphotypes of the maxillary tooth plates can be discerned, which are attributed to ontogenetic variations. A maximum-parsimony analysis was carried out to show that the order Rhynchosauria is characterized by nine cranial and one postcranial character states. The analysis reveals that Otischalkia elderae is invalid and the basal forms, Howesia and Mesosuchus, are closely related. The Mid-Triassic genus Ammorhynchus is more derived and forms a sister group to the Late Triassic subfamily Hyperodapedontinae. Isalorhynchus and Teyumbaita are basal to the pandemic genus Hyperodapedon. Twenty-four characters that are not homoplasious document major patterns of skeletal evolution in rhynchosaurs. From laterally oriented scapula and slender propodials, the postcranial skeleton evolved into a more robust form as is evident from nearly vertical scapula and increase in the robustness of the propodials. Shortening of the femur is noted in the derived Late Triassic forms as exemplified in Hyperodapedon gordoni, Hyperodapedon huxleyi and H. tikiensis.

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