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New Hyperodapedon species (Archosauromorpha, Rhynchosauria) from Triassic of India



From: Ben Creisler
bcreisler@gmail.com

A new online paper:

Debarati Mukherjee and Sanghamitra Ray (2014)
A new Hyperodapedon (Archosauromorpha, Rhynchosauria) from the Upper
Triassic of India: implications for rhynchosaur phylogeny.
Palaeontology (advance online publication)
DOI: 10.1111/pala.12113
http://onlinelibrary.wiley.com/doi/10.1111/pala.12113/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.