Master's Theses

Department

Geosciences

Degree Name

Master of Science (MS)

Abstract

I describe a partial skeleton of a theropod from the Later Jurassic Morrison Formation of Converse County, Wyoming. Collected material included 17 vertebrae, three ribs, two associated left metatarsals and an incomplete ilium of an Allosaurus in a gray silty-mudstone containing conchostraca. Several vertebrae are deformed with transverse processes broken and pressed against the neural spine, or twisted transverse processes from lateral or dorso-venteral compression. The material has evidence of erosion prior to deposition, as well as during postfossilization. I propose the deformation of the vertebrae is due to a demineralization of the bones. The flattened surfaces appear to have been exposed prior to deposition while residing in a low energy alkaline lacustrine environment; causing the vertebrae to become malleable and susceptible to deforming under their own weight. There is also evidence of interaction between two of the vertebrae, where one was resting on top of the other, causing the transverse processes to become twisted. Examination of the neurocentral sutures and length of metatarsal IV indicate this Allosaurus is a maturing sub-adult. This specimen represents the first documented occurrence of Allosaurus in Converse County and the third dinosaur documented from the property.

Date of Award

Spring 2011

Document Type

Thesis

Rights

© 2011 Dennis D. Roth

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