Date Approved


Graduate Degree Type


Degree Name

Health Sciences (M.H.S.)

Degree Program

Biomedical Sciences

First Advisor

Dr. Laura Stroik

Second Advisor

Dr. Melissa Tallman

Third Advisor

Dr. Paul Keenlance

Academic Year



This study examines the relationship between relief index (RFI) on first and second mandibular molars and longevity of the genus. The molars were extracted from small-bodied, arboreal mammals during the late-Paleocene, early-Eocene in the Bighorn Basin in Wyoming. This study site is a well-known location to research and study fossil mammals of this time period. The study was conducted and analyzed at the genus level due to the relatively small number of specimens available and identifiable at the species level. Dietary breadth, or how broad or narrow a dietary preference is for a mammal, is an area of concentration within this study. Dental topography was used as a quantitative measure to study dietary breadth of fossils. Although there are many dental topographic measures, relief index has previously been identified as the best indicator for predicting diet in mammals. This research uses dietary niche breadth (measured as standard deviations of RFI values) to predict for longevity of the fossil genus. By comparing extant taxa and finding a significant difference between generalist and specialist species and their respective values of RFI breadth, this concept was then applied to the fossil sample. The longevities were taken from literature and a least-squared linear regression was conducted. The p-value of the correlation (P=0.465 and R=0.114) indicated that there was not a significant correlation between RFI and longevity. RFI cannot be used to predict longevity of fossil genera. Due to the results of this study, it is now known that there is more that goes into longevity than just dietary niche itself. Although dietary niche may play a part in the extinction of a genus, it is not the sole contributor and must be caused by a combination of other variables.