Date of Award

Fall 2012

Project Type


Program or Major

Earth Sciences: Geology

Degree Name

Master of Science

First Advisor

William C Clyde


The main objective of this study was to determine the most reliable teeth in early Eocene Hyracotherium fossil tooth rows for paleoclimate reconstruction using delta18O values preserved in the tooth enamel. Specimens came from two localities within the Bighorn Basin of Wyoming, D-1204 and D-1583. ANOVA and T-test results generally indicate non-significant differences in mean and variance across tooth rows consisting of m/1, m/2, p/4, and m/3 adult teeth, suggesting any of these teeth may be used for paleoclimate reconstruction purposes as long as sample sizes are large. Additionally, two distinct isotopic patterns were observed across tooth rows, possibly representing late summer/early fall and spring birth seasons. This suggests that Hyracotherium may have given birth multiple times per year and/or could give birth during two different seasons. Such inferences about birth seasons, coupled with dietary delta 13C interpretations, also suggest alternating dry and wet seasons during the lifetime of these individuals.