Archosaur bipedal locomotion

[Ben Creisler <bscreisler@yahoo.com>]

From: Ben Creisler
bscreisler@yahoo.com
 
 
A new advance online paper:
 
K. T. Bates and E. R. Schachner (2011) 
Disparity and convergence in bipedal archosaur locomotion.
Journal of the Royal Society Interface (advance online publication)
doi: 10.1098/​rsif.2011.0687 
http://rsif.royalsocietypublishing.org/content/early/2011/11/21/rsif.2011.0687.abstract?sid=34e22dc3-bad8-4b83-894f-8eeaa01fc612

This study aims to investigate functional disparity in the locomotor apparatus 
of bipedal archosaurs. We use reconstructions of hindlimb myology of extant and 
extinct archosaurs to generate musculoskeletal biomechanical models to test 
hypothesized convergence between bipedal crocodile-line archosaurs and 
dinosaurs. Quantitative comparison of muscle leverage supports the inference 
that bipedal crocodile-line archosaurs and non-avian theropods had highly 
convergent hindlimb myology, suggesting similar muscular mechanics and 
neuromuscular control of locomotion. While these groups independently evolved 
similar musculoskeletal solutions to the challenges of parasagittally erect 
bipedalism, differences also clearly exist, particularly the distinct hip and 
crurotarsal ankle morphology characteristic of many pseudosuchian archosaurs. 
Furthermore, comparative analyses of muscle design in extant archosaurs reveal 
that muscular parameters such as size and
 architecture are more highly adapted or optimized for habitual locomotion than 
moment arms. The importance of these aspects of muscle design, which are not 
directly retrievable from fossils, warns against over-extrapolating the 
functional significance of anatomical convergences. Nevertheless, links 
identified between posture, muscle moments and neural control in archosaur 
locomotion suggest that functional interpretations of osteological changes in 
limb anatomy traditionally linked to postural evolution in Late Triassic 
archosaurs could be constrained through musculoskeletal modelling.