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Dianmeisaurus, new eosauropterygian from Middle Triassic of China (free pdf)



Ben Creisler
bcreisler@gmail.com

A new paper:

SHANG Qing-Hua & LI Chun (2015)
Vertebrata PalAsiatica 53(4): 265-280
A new small-sized eosauropterygian (Diapsida: Sauropterygia) from the
Middle Triassic of Luoping, Yunnan, southwestern China.
http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/201512/t20151204_4487720.html

Free pdf:
http://www.ivpp.cas.cn/cbw/gjzdwxb/xbwzxz/201512/P020151204553839415745.pdf

A new eosauropterygian, Dianmeisaurus gracilis gen. et sp. nov. is
described based on a nearly complete skeleton from the Member II of
Guangling Formation (Anisian) of Luoping County, Yunnan Province. It
is a small-sized (with a total length of less than 50 cm)
sauropterygian with a slender body. This new species is similar
superficially to two other smallsized eosauropterygians,
Diandongosaurus Shang et al., 2011 and Dianopachysaurus Liu et al.,
2011a, which were also collected from the same stratum of Luoping, in
the body proportion, the skull with no contracted snout, and an oval
orbit extremely larger than supratemporal fenestra. However, the new
species is characterized by an extremely narrowed interorbital septum,
the mandibular articulation at the level of occipital condyle, the big
and stout anterolateral process of the clavicle, the proximal part of
the ulna much wider than the distal end, and the presence of 41
presacral vertebrae. Furthermore, the new species differs from
Diandongosaurus in having the preorbital region shorter than the
postorbital region, the prefrontal with no contact of the postfrontal
along the dorsal margin of the orbit, the short mandibular symphysis
with the entrance of the splenial, and the premaxillary and anterior
dentary teeth fang like but not king-sized. Additionally, the
anterolateral process of the clavicle is very sharp and slender in
Diandongosaurus. Compared with the Dianopachysaurus, the new species
is different in having no pachyostosis of the caudal ribs, no more
than three carpal ossifications, and the rounded astragalus. Our
phylogenetic analyses suggest that Dianmeisaurus is probably the
sister group of Diandongosaurus. The two genera, together with the
Majiashanosaurus, Keichousaurus, and Dianopachysaurus are grouped in a
monophyletic clade and phylogenetically more closely related to the
Nothosauroidea than the European pachypleurosaurs (Dactylosaurus,
Anarosaurus, Serpianosaurus, and Neusticosaurus). The coexist of three
small-sized eosauropterygians indicates that sauropterygians were a
highly diversified group of marine reptiles in the Luoping fauna,
Yunnan Province during the early Middle Triassic.