Forearm Posture and Mobility in Quadrupedal Dinosaurs

Dodson, Peter and VanBuren, Collin S. and Bonnan, Matthew (2013) Forearm Posture and Mobility in Quadrupedal Dinosaurs. PLoS ONE, 8 (9). e74842. ISSN 1932-6203 DOI 10.1371/journal.pone.0074842

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Official URL: http://dx.doi.org/10.1371/journal.pone.0074842

Abstract

Quadrupedality evolved four independent times in dinosaurs; however, the constraints associated with these transitions in limb anatomy and function remain poorly understood, in particular the evolution of forearm posture and rotational ability (i.e., active pronation and supination). Results of previous qualitative studies are inconsistent, likely due to an inability to quantitatively assess the likelihood of their conclusions. We attempt to quantify antebrachial posture and mobility using the radius bone because its morphology is distinct between extant sprawled taxa with a limited active pronation ability and parasagittal taxa that have an enhanced ability to actively pronate the manus. We used a sliding semi-landmark, outline-based geometric morphometric approach of the proximal radial head and a measurement of the angle of curvature of the radius in a sample of 189 mammals, 49 dinosaurs, 35 squamates, 16 birds, and 5 crocodilians. Our results of radial head morphology showed that quadrupedal ceratopsians, bipedal non-hadrosaurid ornithopods, and theropods had limited pronation/supination ability, and sauropodomorphs have unique radial head morphology that likely allowed limited rotational ability. However, the curvature of the radius showed that no dinosaurian clade had the ability to cross the radius about the ulna, suggesting parallel antebrachial elements for all quadrupedal dinosaurs. We conclude that the bipedal origins of all quadrupedal dinosaur clades could have allowed for greater disparity in forelimb posture than previously appreciated, and future studies on dinosaur posture should not limit their classifications to the overly simplistic extant dichotomy.

Item Type: Article
Uncontrolled Keywords: NILAREP
Subjects: 04 - Palaeobiology
Divisions: 04 - Palaeobiology
07 - Gold Open Access
Journal or Publication Title: PLoS ONE
Volume: 8
Page Range: e74842
Identification Number: 10.1371/journal.pone.0074842
Depositing User: Sarah Humbert
Date Deposited: 18 May 2015 17:35
Last Modified: 18 May 2015 17:35
URI: http://eprints.esc.cam.ac.uk/id/eprint/3293

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