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Pelvic and hindlimb myology of the basal archosaur Poposaurus gracilis (archosauria: Poposauroidea)

Authors

  • Emma R. Schachner,

    Corresponding author
    1. Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania
    2. Department of Biology, University of Utah, Salt Lake City, Utah
    • Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104
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  • Phillip L. Manning,,

    1. Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania
    2. School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
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  • Peter Dodson

    1. Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, Pennsylvania
    2. School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
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Abstract

The discovery of a largely complete and well preserved specimen of Poposaurus gracilis has provided the opportunity to generate the first phylogenetically based reconstruction of pelvic and hindlimb musculature of an extinct nondinosaurian archosaur. As in dinosaurs, multiple lineages of basal archosaurs convergently evolved parasagittally erect limbs. However, in contrast to the laterally projecting acetabulum, or “buttress erect” hip morphology of ornithodirans, basal archosaurs evolved a very different, ventrally projecting acetabulum, or “pillar erect” hip. Reconstruction of the pelvic and hindlimb musculotendinous system in a bipedal suchian archosaur clarifies how the anatomical transformations associated with the evolution of bipedalism in basal archosaurs differed from that of bipedal dinosaurs and birds. This reconstruction is based on the direct examination of the osteology and myology of phylogenetically relevant extant taxa in conjunction with osteological correlates from the skeleton of P. gracilis. This data set includes a series of inferences (presence/absence of a structure, number of components, and origin/insertion sites) regarding 26 individual muscles or muscle groups, three pelvic ligaments, and two connective tissue structures in the pelvis, hindlimb, and pes of P. gracilis. These data provide a foundation for subsequent examination of variation in myological orientation and function based on pelvic and hindlimb morphology, across the basal archosaur lineage leading to extant crocodilians. J. Morphol., 2011. © 2011 Wiley-Liss, Inc.

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