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Oryctodromeus (ornithopod) digging ability

Ben Creisler

A new online paper:

Jamie L. Fearon & David J. Varricchio (2015)
Morphometric analysis of the forelimb and pectoral girdle of the
Cretaceous ornithopod dinosaur Oryctodromeus cubicularis and
implications for digging.
Journal of Vertebrate Paleontology (advance online publication)

The basal ornithopod Oryctodromeus cubicularis was described as
burrowing due to its discovery in a burrow structure, and the presence
of several morphological features considered consistent with
burrowing. Using traditional and geometric morphometric analyses, the
morphology of the humerus and scapula of ornithopods, basal
ornithischians, and marginocephalians was analyzed to describe and
characterize quantitatively the differences between Oryctodromeus and
other ornithopods. These differences were then compared with the
morphological adaptations for digging in mammals, because there are no
adequate analogues for burrowing in extant archosaurs. A canonical
variates analysis was also conducted on the geometric morphometric
data to determine if phylogeny impacted morphological trends. The
humerus of Oryctodromeus is slightly more robust than other basal
ornithopods, indicating an adaptation for increased force applied to
the humerus. The scapula provides the most compelling morphological
support for digging in Oryctodromeus. The large acromion process and
prominent scapular spine of Oryctodromeus, as well as the large
posteroventrally expanded scapular blade, distinguish the scapula of
Oryctodromeus from those of other ornithopods and would have provided
surface areas for the attachment of the supracoracoideus, deltoideus
clavicularis, and deltoideus scapularis muscles, the latter of which
is important in digging in mammals. These features provide evidence
for specialization for producing burrows by scratch digging.