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English 'abelisauroid' questioned



From: Ben Creisler
bcreisler@gmail.com


Oliver W.M. Rauhut (2012)
A reappraisal of a putative record of abelisauroid theropod dinosaur
from the Middle Jurassic of England.
Proceedings of the Geologists' Association (advance online publication)
http://dx.doi.org/10.1016/j.pgeola.2012.05.008
http://www.sciencedirect.com/science/article/pii/S0016787812000545


Abelisauroidea are a recently recognized clade of theropod dinosaurs
that have a predominantly Gondwanan distribution. Recently, a distal
theropod tibia from the Middle Jurassic of England was identified as
an abelisauroid, representing one of the oldest records of the group
in general and the only Jurassic occurrence in Europe. On this basis,
rapid radiation of abelisauroid and a global distribution of this
clade in the Jurassic were suggested. Here, the specimen in question
is re-examined and the characters used for referral to the
Abelisauroidea are re-evaluated. None of the proposed characters can
be demonstrated to represent abelisauroid synapomorphies and all have
a wider distribution; especially coelurosaurian theropods, which are
known from contemporaneous beds in England, frequently show the same
character combination. Thus, there is currently no secure evidence for
the occurrence of abelisauroids in the Jurassic of the northern
Hemisphere, and the early evolution of this clade remains poorly
known. Furthermore, other fragmentarily known taxa previously referred
to Abelisauroidea based on putative synapomorphies of the distal
tibia, such as Ozraptor and Austrocheirus, should be considered as
Theropoda indet.