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Concavispina (Thalattosauria) osteology



From: Ben Creisler
bcreisler@gmail.com


In the new issue of the Journal of Paleontology:


Jun Liu, Li-Jun Zhao, Chun Li, and Tao He (2013)
Osteology of Concavispina biseridens (Reptilia, Thalattosauria) from
the Xiaowa Formation (Carnian), Guanling, Guizhou, China.
Journal of Paleontology 87(2): 341-350. 2013
doi: http://dx.doi.org/10.1666/12-059R1.1
http://www.bioone.org/doi/abs/10.1666/12-059R1.1

A thalattosaur taxon, Concavispina biseridens, was recently named and
briefly described. It is described here in detail and compared with
other thalattosaurs, especially Xinpusaurus. Concavispina is
characterized by a long skull, measuring approximately half the length
of presacral portion of the vertebral column, two rows of blunt teeth
on the anterior part of the maxilla, and neural spines that have
convex anterior or posterior margins and V-shaped notches in their
dorsal margins. Concavispina differs from all thalattosaurs except
Xinpusaurus in that the anterior end of the maxilla is curved
dorsally, less than five cervical vertebrae are present, and the
proximal end of the humerus is wider than the distal end. Phylogenetic
analysis of 40 characters suggests that Miodentosaurus occupies a
basal position within Askeptosauridea, Paralonectes is the basalmost
member of Thalattosauridea, Concavispina may form a clade with
Xinpusaurus, and Chinese thalattosaurs do not have a close
relationship with eastern Pacific forms as suggested by previous
studies. Concavispina may have been similar to Xinpusaurus in overall
locomotor style, but probably had a poorer swimming ability.
Concavispina likely differed from Xinpusaurus in diet, for example by
depending on softer food.