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British Triassic island fauna revealed in fissures



From: Ben Creisler
bcreisler@gmail.com


A new online paper:


Tamara van den Berg, David I. Whiteside, Pedro Viegas, Remmert
Schouten & Michael J. Benton (2012)
The Late Triassic microvertebrate fauna of Tytherington, UK.
Proceedings of the Geologists' Association (advance online publication)
http://dx.doi.org/10.1016/j.pgeola.2012.05.003
http://www.sciencedirect.com/science/article/pii/S0016787812000375



The Late Triassic fissure fills from the region of Bristol, SW England
and S Wales, preserve unique assemblages of small vertebrates derived
from an archipelago of palaeo-islands that document aspects of a
critical transition in the history of terrestrial ecosystems.
Tytherington Quarry, in south Gloucestershire, is the site of several
fossiliferous fissures, all dated as Rhaetian (terminal Triassic), and
source of abundant remains of the ‘Bristol dinosaur’, Thecodontosaurus
antiquus. In addition, the fissure sediments have yielded previously
unreported microvertebrate assemblages, including over 400 jaw remains
from three genera of sphenodontians and 100 archosaur teeth assigned
to 15 morphotypes. The land fauna is dominated by sphenodontians, with
Diphydontosaurus by far the most common form, followed by Clevosaurus,
then the sauropodomorph dinosaur Thecodontosaurus, and then the
sphenodontian Planocephalosaurus. There are, in addition, rare remains
of contemporaneous bony fishes, as well as fossils apparently reworked
from the Carboniferous limestones, namely conodonts, holocephalian
(chimaeroid) teeth, and a shark tooth. Many typical latest Triassic
animals, such as temnospondyls, phytosaurs, aetosaurs, rauisuchians,
plateosaurids and dicynodonts are not represented at Tytherington,
perhaps because these generally larger animals did not live on the
palaeo-island, or because their carcasses could not fit into the
fissures. The absence of tritylodonts and early mammals is, however,
less easy to explain on the basis of size, although it is known that
these forms were abundant here by the Early Jurassic.