Taxonomic revision of latest Cretaceous North american basal neonithischian taxa and a phylogenetic analysis of basal ornithischian relationships

dc.contributor.advisorClarke, Julia A.
dc.creatorBoyd, Clint Aaroenen
dc.date.accessioned2013-11-08T20:59:42Zen
dc.date.issued2012-05en
dc.date.submittedMay 2012en
dc.date.updated2013-11-08T20:59:42Zen
dc.descriptiontexten
dc.description.abstractThe systematic relationships of basal ornithischian dinosaurs remain contentious, especially the position of basal neornithischians (i.e., ‘hypsilophodontids’). Prior analyses of basal ornithischian relationships have been hampered by the fact that the hypodigm material of many basal neornithischian taxa is fragmentary, denying access to character data crucial to resolving their relationships. The recent discovery of several new basal neornithischian taxa and the referral of more complete specimens to known taxa provide important new data pertinent to resolving these relationships. The results of this study supplement those recent advances by improving our understanding of the anatomy and systematic relationships of basal neornithischian taxa from the Late Cretaceous of North America. These new insights are accomplished through a taxonomic revision of the Maastrichtian taxa Bugenasaura and Thescelosaurus, a detailed anatomical description of the cranial anatomy of Thescelosaurus neglectus based on the referral of a specimen that includes a nearly complete skull (NCSM 15728), and description of a new basal neornithischian taxon from the Kaiparowits Formation (Campanian) of Utah. All of these new data are compiled into a dataset composed of 255 characters for 65 terminal taxa (all species exemplars) focused on assessing basal ornithischian relationships. The recovered strict consensus topology is the most highly resolved, stratigraphically congruent phylogenetic hypothesis of basal ornithischian relationships yet proposed. This analysis places all basal neornithischians except Hypsilophodon foxii outside of Cerapoda, substantially reducing the taxonomic contents of Ornithopoda. A new clade containing fourteen basal neornithischian taxa is recovered as the sister taxon to Cerapoda and includes all North American basal neornithischians from the Cretaceous. The historical biogeography of Ornithischia is also reconstructed using a method that incorporates time calibrated branch lengths that represent the implied missing fossil record of each taxon. The results of this analysis support two dispersals of neornithischian taxa into South America during the Cretaceous: one consisting of basal iguanodontians dispersing from Australia (possibly via Antarctica) and a second consisting of basal neornithischians dispersing from Asia through North America.en
dc.description.departmentGeological Sciencesen
dc.embargo.lift5/1/2013en
dc.embargo.terms5/1/2013en
dc.format.mimetypeapplication/pdfen
dc.identifier.urihttp://hdl.handle.net/2152/22088en
dc.language.isoen_USen
dc.subjectOrnithischianen
dc.subjectMaastrichtianen
dc.subjectNeornithischianen
dc.subjectPhylogenyen
dc.subjectSkaladromeusen
dc.subjectThescelosaurusen
dc.subjectCretaceousen
dc.subjectBasalen
dc.subjectNorth Americaen
dc.subjectTaxonomyen
dc.titleTaxonomic revision of latest Cretaceous North american basal neonithischian taxa and a phylogenetic analysis of basal ornithischian relationshipsen
thesis.degree.departmentGeological Sciencesen
thesis.degree.disciplineGeological Sciencesen
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen
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