The evolution,development and skeletal identity of the crocodylian pelvis: Revisiting a forgotten scientific debate |
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Authors: | Leon P.A.M. Claessens Matthew K. Vickaryous |
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Affiliation: | 1. Department of Biology, College of the Holy Cross, One College Street, Worcester, Massachusetts 01610;2. Department of Geology, Netherlands Centre for Biodiversity Naturalis, Darwinweg 2, 2333 CR, Leiden, The Netherlands;3. Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, 50 Stone Road, Guelph, Ontario, Canada N1G 2W1 |
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Abstract: | Unlike most tetrapods, in extant crocodylians the acetabulum is formed by only two of the three skeletal elements that constitute the pelvis, the ilium, and ischium. This peculiar arrangement is further confused by various observations that suggest the crocodylian pelvis initially develops from four skeletal elements: the ilium, ischium, pubis, and a novel element, the prepubis. According to one popular historical hypothesis, in crocodylians (and many extinct archosaurs), the pubis fuses with the ischium during skeletogenesis, leaving the prepubis as a distinct element, albeit one which is excluded from the acetabulum. Whereas the notion of a distinct prepubic element was once a topic of considerable interest, it has never been properly resolved. Here, we combine data gleaned from a developmental series of Alligator mississippiensis embryos, with a revised interpretation of fossil evidence from numerous outgroups to Crocodylia. We demonstrate that the modern crocodylian pelvis is composed of only three elements: the ilium, ischium, and pubis. The reported fourth pelvic element is an unossified portion of the ischium. Interpretations of pelvic skeletal homology have featured prominently in sauropsid systematics, and the unambiguous identification of the crocodylian pubis provides an important contribution to address larger scale evolutionary questions associated with locomotion and respiration. J. Morphol. , 2012. © 2012 Wiley Periodicals, Inc. |
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Keywords: | Archosauria crocodylia Alligator mississippiensis pubis prepubis pelvis |
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