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Triassic marine reptiles from China: Kwangsisaurus date & Chaohusaurus environment

Ben Creisler

Two recent papers with free pdfs about Triassic marine reptiles from
China. Main texts are in Chinese.

SHANG Qing-Hua, LIU Jun, XU Guang-Hui & WANG Li-Ting (2014)
The age of Triassic marine reptile Kwangsisaurus orientalis
(Sauropterygia) from Wuming, Guangxi, China.
Vertebrata PalAsiatica 52(4):  381-389
free pdf:

The holotype of Kwangsisaurus orientalis Young, 1959 is the only
Triassic marine  reptile specimen known from Guangxi Zhuang Autonomous
Region in southern China. This  fossil was collected from Wuming
County in 1950s. The exact provenance of the specimen is  unclear, but
it has long been regarded as an Early Triassic sauropterygian
following Young’s  original description (Li, 2006b; Li et al., 2008;
Zhao et al., 2008). The uncertainty regarding  its age has introduced
confusion into the studies of biogeography and evolutionary history of
 Chinese Triassic sauropterygians. Based on recent field work and the
help of several local geologists who have knowledge  of the specimen’s
history, we have determined that the holotype of K. orientalis was
from a  quarry situated 2 km southeast of Fupeng, Suliang Village,
Xianhu Township, Wuming County  (Fig. 1). The type specimen was
obtained from a fossiliferous bed within thin-bedded marlite,  which
is considered as the lower part of the Banna Formation based on
lithological features.  This fossiliferous bed contains abundant
ammonites such as Balatonites, Protrachyceras, and  Leiophyllites, in
addition to some fragmentary vertebrate bones and plant debris (Figs.
1, 2).  It can be identified as Middle Triassic based on the
ammonites. Above it lies a tuff layer with  a thickness of 10-20 cm,
which is a marker bed of the Banna Formation. The tuff layer was
dated to (244.2±0.7) Ma by High-precision SIMS zircon U-Pb analyses,
making the age of K.  orientalis Pelsonian (Anisian, Middle Triassic).
The Anisian age of K. orientalis is concordant with its
reidentification as a pistosaurid  by Rieppel (1999a). This age
assignment also refutes the longstanding interpretation that
sauropterygians appeared in the Youjiang Basin during the Early
Triassic, and shows instead  that K. orientalis is almost synchronous
with the Panxian marine reptile fauna. The Chinese  record of
sauropterygians shows that this group had dispersed over a large area
and adapted to  a diverse range of environments by the Anisian.


Zhang Yuying, Jiang Dayong, Fu Wanlu, Ji Cheng & Sun Zuoyu (2014)
Microfacies characteristics of the Lower Triassic containing
Chaohusaurus fauna in Chaohu area, Anhui Province and its
Journal of Palaeogeography 16(5): 761-768
DOI: 10.7605/gdlxb.2014.05.61

pdf is free

The Early Triassic Chaohusaurus fauna was found at No.598-630 layers
at the top of the Middle Member-the bottom of the Upper Member of the
Nanlinghu Formation in Majiashan section of Chaohu area,Anhui
Province. Based on the microfacies characteristics and the carbon and
oxygen isotope analysis,the sedimentary environment of the fossil beds
where the Chaohusaurus fauna had occurred was studied. 4microfacies
types were recognized from the studied layers,which contained the
red-grey thick nodular limestone with spicules-bivalves,the gray
bioclastic-argillaceous micrite limestone,the gray laminated
argillaceous micrite limestone,and the light gray micrite
limestone,respectively. It was indicated that the sedimentary
environment of the fossil beds was from the foot of the outer
ramp-abyssal basin to the outer ramp. The values of the δ13C and δ18O
are generally low in the whole of fossil beds. Combined with the above
characteristics,it might be inferred that the Chaohusaurus fauna was
living in the outer ramp zone with low-energy,less numbers and types
of the biocoenose,and high seawater temperature.