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Marine vertebrate biotas from Triassic of China

From: Ben Creisler

A new online paper:

Michael J. Benton, Qiyue Zhang, Shixue Hu, Zhong-Qiang Chen, Wen Wen,
Jun Liu, Jinyuang Huang, Changyong Zhou, Tao Xie, Jinnan Tong & Brian
Choo (2013)
Exceptional vertebrate biotas from the Triassic of China, and the
expansion of marine ecosystems after the Permo-Triassic mass
Earth-Science Reviews (advance online publication)

The Triassic was a time of turmoil, as life recovered from the most
devastating of all mass extinctions, the Permo-Triassic event 252
million years ago. The Triassic marine rock succession of southwest
China provides unique documentation of the recovery of marine life
through a series of well dated, exceptionally preserved fossil
assemblages in the Daye, Guanling, and Falang groups. New work shows
the richness of the faunas of fishes and reptiles, and that recovery
of vertebrate faunas was delayed by harsh environmental conditions and
then occurred rapidly in the Anisian. The key faunas of fishes and
reptiles come from a limited area in eastern Yunnan and western
Guizhou provinces, and these may be dated relative to shared
stratigraphic units, and their palaeoenvironments reconstructed. The
Luoping and Panxian biotas, both from the Guanling Formation, are
dated as Anisian (Pelsonian) on the basis of conodonts and radiometric
dates, the former being slightly older than the latter. The Xingyi
biota is from the Zhuganpo Formation, and is Ladinian or early
Carnian, while the Guanling biota is from the overlying Xiaowa
Formation, dated as Carnian. The first three biotas include extensive
benthos and burrowing in the sediments, and they were located in
restricted basins close to shore. Further, even though the Luoping and
Panxian biotas are of similar age, their faunas differ significantly,
reflecting perhaps palaeogeographically isolated basins. Between the
time of the Xingyi and Guanling biotas, there was a major
transgression, and the Guanling biota is entirely different in
character from the other three, being dominated by pelagic forms such
as large floating crinoids attached to logs, very large ichthyosaurs
and thalattosaurs, and pseudoplanktonic bivalves, with no benthos and
no burrowing. Phylogenetic study of the fishes and marine reptiles
shows apparently explosive diversification among 20 actinopterygian
lineages very early in the Early Triassic, but a later expansion of
marine reptile groups, in the late Olenekian and early Anisian. This
offset in diversification patterns is matched by comparisons of
feeding guild categories and body size data. New research tools will
shed considerable light on the phylogenetic and ecological
implications of recovery of mairne vertebrates in the Triassic.