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Systematics, evolution, and biogeography of the ankylosaurid dinosaurs Open Access


Other title
Vertebrate Palaeontology
Vertebrate Paleontology
Type of item
Degree grantor
University of Alberta
Author or creator
Arbour, Victoria M
Supervisor and department
Currie, Philip (Biological Sciences)
Examining committee member and department
Sperling, Felix (Biological Sciences)
Murray, Alison (Biological Sciences)
Theodor, Jessica (Biological Sciences - University of Calgary)
Acorn, John (Renewable Resources)
Department of Biological Sciences
Systematics and Evolution
Date accepted
Graduation date
Doctor of Philosophy
Degree level
The Ankylosauria is a group of herbivorous, quadrupedal, armoured dinosaurs subdivided into at least two major clades, the Ankylosauridae and the Nodosauridae. The most derived members of the Ankylosauridae had a unique tail club formed from modified, tightly interlocking distal caudal vertebrae and enlarged osteoderms that envelop the terminus of the tail. A review of all known ankylosaurid species, as well as ankylosaurs of uncertain affinities, was undertaken in order to conduct a revised phylogenetic analysis of the clade. Sources of morphological variability were investigated using the relatively large number of specimens referred to Euoplocephalus tutus. Taphonomic distortion can influence the morphology of certain features which were thought to be taxonomically significant. However, the cranial ornamentation of ankylosaurs can be useful for distinguishing species and genera and should not be discounted as being too intraspecifically variable. The overall shape, size, and pattern of the frontonasal caputegulae, the number and shapes of the caputegulae that rim the skull in dorsal view (the nuchal, supraorbital, lacrimal, loreal, and supranarial caputegulae), and the general shapes of the squamosal and quadratojugal horns are all taxonomically important features. Information from the review of Euoplocephalus allows for the recognition of new ankylosaurid species, synonymization of other species, and resurrection of some previously synonymized species. The revised phylogenetic analysis resulted in a monophyletic Ankylosauridae consisting of Aletopelta, Gastonia, Gobisaurus, Liaoningosaurus, Shamosaurus, and a suite of derived ankylosaurids (Ankylosaurinae). There is convincing evidence for the presence of nodosaurids in Asia during the Early Cretaceous. In the mid Cretaceous, Asian nodosaurids were replaced by ankylosaurine ankylosaurids. Modifications to the tail of ankylosaurines occurred at this time, with distinct handle vertebrae appearing potentially as early as the Albian, with Liaoningosaurus. The large osteodermal knob did not appear until the Late Cretaceous. Ankylosaurines migrated into North America from Asia between the Albian and Turonian, where they diversified into a clade of ankylosaurines characterized by arched snouts and numerous flat caputegulae. There is no evidence for any ankylosaurids in Gondwana; the Ankylosauridae appears to be completely restricted to Asia and North America.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Arbour VM, Currie PJ. 2012. Analyzing taphonomic deformation of ankylosaur skulls using retrodeformation and finite element analysis. PLOS ONE 7(6):e39323.Arbour VM, Currie PJ. 2013. Euoplocephalus tutus and the diversity of ankylosaurid dinosaurs in the Late Cretaceous of Alberta, Canada, and Montana, USA. PLOS ONE 8(5):e62421.Arbour VM, Currie PJ. 2013. The taxonomic identity of a nearly complete ankylosaurid dinosaur skeleton from the Gobi Desert of Mongolia. Cretaceous Research 46:24-30.

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