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1 March 2011 A Review of Pelvic Shield Morphology in Ankylosaurs (Dinosauria: Ornithischia)
Victoria M. Arbour, Michael E. Burns, Philip J. Currie
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The pelvic shield of ankylosaurian dinosaurs refers to an area of osteoderms lacking differentiated transverse bands over the pelvic region and it is used as a diagnostic character for various ankylosaur groups. The pelvic shield character varies across ankylosaur taxa but is typically coded as a binary character or is excluded from phylogenetic analyses, which obscures evolutionary trends and relationships. This study investigates for the first time pelvic shield morphology in a stratigraphic and geographic context. This paper comprehensively reviews pelvic shield morphology with firsthand observations of specimens, and proposes three categories of pelvic shield morphology. Category 1 pelvic shields have un-fused but tightly interlocking osteoderms. Category 2 pelvic shields have fused osteoderms forming rosettes and are restricted to the Late Jurassic to mid Cretaceous of North America and Europe. Category 3 pelvic shields have fused polygonal osteoderms of similar size, and are found in the mid- to Late Cretaceous of North America. Although the pelvic shield is used to characterize the Polacanthidae, an interpretation supported by this review, the validity of such a clade is dependent upon a global parsimony analysis incorporating this character. Future analyses of the Ankylosauria should incorporate a more detailed treatment of the pelvic shield to determine its diagnostic value within the group.

Victoria M. Arbour, Michael E. Burns, and Philip J. Currie "A Review of Pelvic Shield Morphology in Ankylosaurs (Dinosauria: Ornithischia)," Journal of Paleontology 85(2), 298-302, (1 March 2011).
Accepted: 1 October 2010; Published: 1 March 2011

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