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Australovenator Forearm Range of Motion



Ben Creisler
bcreisler@gmail.com

In PLoS ONE:

Matt A. White, Phil R. Bell, Alex G. Cook, David G. Barnes, Travis R.
Tischler, Brant J. Bassam, David A. Elliott
Forearm Range of Motion in Australovenator wintonensis (Theropoda,
Megaraptoridae).
PLoS ONE 10(9): e0137709.
doi:10.1371/journal.pone.0137709
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137709


The hypertrophied manual claws and modified manus of megaraptoran
theropods represent an unusual morphological adaptation among
carnivorous dinosaurs. The skeleton of Australovenator wintonensis
from the Cenomanian of Australia is among the most complete of any
megaraptorid. It presents the opportunity to examine the range of
motion of its forearm and the function of its highly modified manus.
This provides the basis for behavioural inferences, and comparison
with other Gondwanan theropod groups. Digital models created from
computed tomography scans of the holotype reveal a humerus range of
motion that is much greater than Allosaurus, Acrocanthosaurus,
Tyrannosaurus but similar to that of the dromaeosaurid Bambiraptor.
During flexion, the radius was forced distally by the radial condyle
of the humerus. This movement is here suggested as a mechanism that
forced a medial movement of the wrist. The antebrachium possessed a
range of motion that was close to dromaeosaurids; however, the unguals
were capable of hyper-extension, in particular manual phalanx I-2,
which is a primitive range of motion characteristic seen in
allosaurids and Dilophosaurus. During flexion, digits I and II
slightly converge and diverge when extended which is accentuated by
hyperextension of the digits in particular the unguals. We envision
that prey was dispatched by its hands and feet with manual phalanx I-2
playing a dominant role. The range of motion analysis neither confirms
nor refutes current phylogenetic hypotheses with regards to the
placement of Megaraptoridae; however, we note Australovenator
possessed, not only a similar forearm range of motion to some
maniraptorans and basal coelurosaurs, but also similarities with
Tetanurans (Allosauroids and Dilophosaurus).