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Oryctodromeus (Cretaceous ornithopod) forelimb musculature reconstruction and digging ability



Ben Creisler
bcreisler@gmail.com


A new paper:

Jamie L. Fearon & David J. Varricchio (2016)
Reconstruction of the forelimb musculature of the Cretaceous
ornithopod dinosaur Oryctodromeus Cubicularis: implications for
digging.
Journal of Vertebrate Paleontology (advance online publication)
DOI:10.1080/02724634.2016.1078341
https://urldefense.proofpoint.com/v2/url?u=http-3A__&d=CwIBaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=x82f3Wlkwtmbr1z8IAt9jA&m=_rRWvQGhzj2M3eHi7WFKNxr35D_VSJ4tDOvBQlTGv0Q&s=-DfdpBygyv70X7J1Mq-wuFats0samceADyBjhGRplEs&e=
  www.tandfonline.com/doi/full/10.1080/02724634.2016.1078341

Taphonomic and morphological evidence suggests that Oryctodromeus
cubicularis, a basal ornithopod dinosaur from the mid-Cretaceous of
Montana, constructed burrows by digging with its forelimbs.
Reconstruction of the forelimb musculature of Oryctodromeus was
carried out using the extant phylogenetic bracket method, with
crocodilians and ratites as the extant analogues, aided by the
presence of osteological correlates in Oryctodromeus and other
ornithopods. Although reconstructions directly from the extant
phylogenetic bracket are relatively conservative, the reconstruction
elucidates several potential features related to burrowing. The
prominent muscle groups used in burrowing in mammals are the
deltoideus scapularis, teres major, latissimus dorsi, and triceps
longus. In Oryctodromeus, the deltoideus scapularis, and equivocally
the teres major, has broad origin on the strongly posteroventrally
expanded distal scapular blade. Neither the origin of the deltoideus
scapularis nor that of the teres major produces osteological
correlates in extant taxa or Oryctodromeus; however, the ventrally
expanded posterior scapular blade would have increased attachment area
for the origin of these muscle groups. The presence of the latissimus
dorsi is supported by the extant phylogenetic bracket but produces no
osteological correlates in Oryctodromeus. The triceps longus
originates posterior to the glenoid and inserts on the ulna. Due to
the proximity of the triceps longus origin to the glenoid, the triceps
longus likely did not provide strong muscle action. Because many
mammals and reptiles produce burrows without any morphological
specialization, the limited specializations of the deltoideus
scapularis and potentially the teres major sufficiently support
burrowing capabilities in Oryctodromeus.

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