Largocephalosaurus (saurosphargid diapsid), new species from Triassic of China

[Ben Creisler <bcreisler@gmail.com>]

From: Ben Creisler
bcreisler@gmail.com

A new online paper:


Chun Li, Da-Yong Jiang, Long Cheng, Xiao-Chun Wu and Olivier Rieppel (2013)
A new species of Largocephalosaurus (Diapsida: Saurosphargidae), with
implications for the morphological diversity and phylogeny of the
group.
Geological Magazine (advance online publication)
DOI: http://dx.doi.org/10.1017/S001675681300023X
http://128.232.233.5/action/displayAbstract?fromPage=online&aid=8920775&fulltextType=RA&fileId=S001675681300023X


Largocephalosaurus polycarpon Cheng et al. 2012 was erected after the
study of the skull and some parts of a skeleton and considered to be
an eosauropterygian. Here we describe a new species of the genus,
Largocephalosaurus qianensis, based on three specimens. The new
species provides many anatomical details which were described only
briefly or not at all in the type species, and clearly indicates that
Largocephalosaurus is a saurosphargid. It differs from the type
species mainly in having three premaxillary teeth, a very short
retroarticular process, a large pineal foramen, two sacral vertebrae,
and elongated small granular osteoderms mixed with some large ones
along the lateral most side of the body. With additional information
from the new species, we revise the diagnosis and the phylogenetic
relationships of Largocephalosaurus and clarify a set of diagnostic
features for the Saurosphargidae Li et al. 2011. Largocephalosaurus is
characterized primarily by an oval supratemporal fenestra, an elongate
dorsal ‘rib-basket’, a narrow and elongate transverse process of the
dorsal vertebrae, and the lack of a complete dorsal carapace of
osteoderms. The Saurosphargidae is distinct mainly in having a
retracted external naris, a jugal–squamosal contact, a large
supratemporal extensively contacting the quadrate shaft, a leaf-like
tooth crown with convex labial surface and concave lingual surface, a
closed dorsal ‘rib-basket’, many dorsal osteoderms, a large
boomerang-like or atypical T-shaped interclavicle. Current evidence
suggests that the Saurosphargidae is the sister-group of the
Sauropterygia and that Largocephalosaurus is the sister-group of the
Saurosphargis–Sinosaurosphargis clade within the family.