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A computational analysis of locomotor anatomy and body mass evolution in Allosauroidea (Dinosauria, Theropoda)

Karl T. Bates, Roger B. J. Benson and Peter L. Falkingham
A computational analysis of locomotor anatomy and body mass evolution in Allosauroidea (Dinosauria, Theropoda)
Paleobiology (June 2012) 38 (3): 486-507

Abstract

We investigate whether musculoskeletal anatomy and three-dimensional (3-D) body proportions were modified during the evolution of large (>6000 kg) body size in Allosauroidea (Dinosauria: Theropoda). Three adaptations for maintaining locomotor performance at large body size, related to muscle leverage, mass, and body proportions, are tested and all are unsupported in this analysis. Predictions from 3-D musculoskeletal models of medium-sized (Allosaurus) and large-bodied (Acrocanthosaurus) allosauroids suggest that muscle leverage scaled close to isometry, well below the positive allometry required to compensate for declining muscle cross-sectional area with increasing body size. Regression analyses on a larger allosauroid data set finds slight positive allometry in the moment arms of major hip extensors, but isometry is included within confidence limits. Contrary to other recent studies of large-bodied theropod clades, we found no compelling evidence for significant positive allometry in muscle mass between exemplar medium- and large-bodied allosauroids. Indeed, despite the uncertainty in quantitative soft tissue reconstruction, we find strong evidence for negative allometry in the caudofemoralis longus muscle, the single largest hip extensor in non-avian theropods. Finally, we found significant inter-study variability in center-of-mass predictions for allosauroids, but overall observe that consistently proportioned soft tissue reconstructions produced similar predictions across the group, providing no support for a caudal shift in the center of mass in larger taxa that might otherwise reduce demands on hip extensor muscles during stance. Our data set provides further quantitative support to studies that argue for a significant decline in locomotor performance with increasing body size in non-avian theropods. However, although key pelvic limb synapomorphies of derived allosauroids (e.g., dorsomedially inclined femoral head) evolved at intermediate body sizes, they may nonetheless have improved mass support.


ISSN: 0094-8373
EISSN: 1938-5331
Coden: PALBBM
Serial Title: Paleobiology
Serial Volume: 38
Serial Issue: 3
Title: A computational analysis of locomotor anatomy and body mass evolution in Allosauroidea (Dinosauria, Theropoda)
Affiliation: University of Liverpool, Department of Musculoskeletal Biology, Liverpool, United Kingdom
Pages: 486-507
Published: 201206
Text Language: English
Publisher: Paleontological Society, Lawrence, KS, United States
References: 57
Accession Number: 2012-073235
Categories: Vertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Supplemental information/data is available in the online version of this article
Illustration Description: illus. incl. 4 tables
Secondary Affiliation: University of Cambridge, GBR, United KingdomUniversity of Manchester, GBR, United Kingdom
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, The Paleontological Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201238
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