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Phylogenetic and Palaeobiogeographical Analysis of Tylosaurinae (Squamata: Mosasauroidea) Open Access


Other title
Type of item
Degree grantor
University of Alberta
Author or creator
Jimenez Huidobro, Paulina A
Supervisor and department
Caldwell, Michael W. (Biological Sciences)
Examining committee member and department
Holmes, Robert (Biological Sciences)
Murray, Alison (Biological Sciences)
Acorn, John (Renewable Resources)
Evans, David (Royal Ontario Museum)
Department of Biological Sciences
Systematics and Evolution
Date accepted
Graduation date
2016-06:Fall 2016
Doctor of Philosophy
Degree level
Mosasaurs were a successful and diverse group of marine lizard that existed during the Cretaceous Period, spanning a period of geologic time from the Turonian to Maastrichtian. Their fossils are found around the world, although most records are known from the Northern Hemisphere. The Southern Hemisphere record of mosasaurs is poor and incomplete. The mosasaur clade/subfamily Tylosaurinae is characterized by an elongated rostrum, which does not bear teeth. While the genus Tylosaurus is known from hundreds of specimens collected from the Niobrara Formation in Kansas, and now from dozens of specimens from other localities around North America, the alpha taxonomy of the genus has remained confused and poorly diagnosed. This means that very little was understood about the classification and phylogenetic relationships of North American tylosaurine mosasaurs, not to mention global tylosaurine mosasaurs. This problem originated with the historical rivalry between E.D. Cope and O.C. Marsh during the 1800s, and hopefully, in part, it is resolved in the research reported in this thesis. This thesis reports on a reassessment and re-description of specimens both assigned to the Tylosaurinae, and thus that were newly discovered during this research project. The goal was to refine and improve the understanding of the evolution and palaeogeography of the clade. The clade Tylosaurinae was proved as monophyletic, as well as one of the genus: Tylosaurus. The concept of ‘tylosaurine’ changed from a diverse group with three genera and eleven species, to a more limited concept of the group, consisting in two genera and seven species. The geographic and temporal distribution of the two genera, and the subfamily, where established as upper Turonian to lower Maastrichtian of the North Atlantic Basin for the genus Tylosaurus, while a cosmopolitan distribution, between the middle Santonian and lower Maastrichtian was determined for Taniwhasaurus. The thesis is divided in seven chapters, starting with a general introduction, followed by reassessments and re-descriptions of specific taxa, with a phylogenetic and palaeobiological analysis of the Tylosaurinae, and final conclusions regarding the results of the project.
This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
Citation for previous publication
Jiménez-Huidobro, P. and Caldwell, M. W. 2016. Reassessment and reassignment of the Early Maastrichtian mosasaur Hainosaurus bernardi Dollo, 1885, to Tylosaurus Marsh, 1872. Journal of Vertebrate Paleontology 36 (3): e1096275-12.

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