Date of Award

Spring 1-1-2013

Document Type


Degree Name

Master of Science (MS)


Museum and Field Studies

First Advisor

Jaelyn J. Eberle

Second Advisor

Christy M. McCain

Third Advisor

Peter Robinson


The Paleocene-Eocene Thermal Maximum (PETM) represents a rapid global warming at the Paleocene-Eocene (PE) boundary. In the Powder River Basin, northeast Wyoming, strata of the "Wasatch" formation contain a terrestrial mammalian fauna spanning the PETM. I tested whether the dwarfing of mammalian taxa observed by researchers in the Bighorn Basin occurs in the Powder River Basin (and is therefore a more regional pattern).

Using tooth crown area as a proxy for body size, I looked for patterns of body size change during the PETM. Arctodontomys, Cantius, Apheliscus, Hyopsodus, and Paramys all suggest that dwarfing occurred in the Powder River Basin during the Wa0 interval. However, Acritoparamys seems to show an increase in body size from late Clarkforkian to earliest Wasatchian (Wa0) time. I also document the first occurrence of the cylindrodontid rodent Tuscahomys cf. T. majori and describe four distinct rodent lower incisor morphologies.