Chalawan, new pholidosaurid crocodilian from Cretaceous of Thailand

[Ben Creisler <bcreisler@gmail.com>]

From: Ben Creisler
bcreisler@gmail.com


A new online paper:



Jeremy E. Martin, Komsorn Lauprasert, Eric Buffetaut, Romain Liard &
Varavudh Suteethorn (2013)
A large pholidosaurid in the Phu Kradung Formation of north-eastern Thailand.
Palaeontology (advance online publication)
DOI: 10.1111/pala.12086
http://onlinelibrary.wiley.com/doi/10.1111/pala.12086/abstract

In the early 1980s, the remains of a large crocodilian, consisting of
a nearly complete lower jaw, were referred to a distinct species of
Sunosuchus, S. thailandicus. The specimen was recovered from a
road-cut near Nong Bua Lamphu, north-eastern Thailand, in the upper
part of the continental Phu Kradung Formation, and then considered
Early to Middle Jurassic in age. Since then, this age has been revised
and most of the formation is now considered Early Cretaceous, although
a Late Jurassic age is possible for its lowermost part. Here, we
report for the first time cranial elements associated with mandibular
remains assignable to ‘S’. thailandicus. An attribution to
Pholidosauridae is proposed on the basis of premaxillary morphology,
and the original referral of this taxon to the goniopholidid
Sunosuchus is discarded. A new genus name Chalawan now designates the
originally described material of S. thailandicus. Nevertheless, the
newly described specimen shares a characteristic with both
‘traditional’ Goniopholididae and Pholidosauridae: the presence of a
depression located on the lateral wall of the maxilla and jugal. A
phylogenetic analysis confirms the inclusion of both Goniopholididae
and Pholidosauridae into a common clade, Coelognathosuchia tax. nov.
Although the new Thai skull is much fragmented, its original shape is
reconstructed and is compared with other pholidosaurid genera, namely
Elosuchus, Meridiosaurus, Oceanosuchus, Pholidosaurus, Sarcosuchus and
Terminonaris. The presence of the genus Sunosuchus being highly
questionable in Thailand, it cannot be used as evidence to link the
Chinese and Indochinese blocks. Instead, the recognition of a
freshwater pholidosaurid in a continental formation of the Indochinese
block suggests that early in their evolutionary history, these
crocodilians, already known from Europe, Africa and South America,
were more widely distributed along the northern margin of the Tethys
than previously recognized.