Meeting Abstract

P1-57   -   Bite force estimates in geomyoid rodents: ecological and evolutionary implications Ball, MP*; Calede, JJ; The Ohio State University, Marion, OH; The Ohio State University, Marion, OH ball.2164@buckeyemail.osu.edu

Geomyoidea is a highly diverse clade of rodents containing both geomyids (pocket gophers) and heteromyids (kangaroo rats, pocket mice, and their relatives). The taxonomic diversity of this group is associated with its great disparity in morphology. We focus on one aspect of morphology: bite force (BF). We used measurements of the lower incisor to estimate BF and cranial/toothrow length to estimate body size. We used these data to calculate the bite force quotient (BFQ) for each specimen and each taxon. We estimated the BF of 351 specimens representing 37 species and all genera of extant geomyoids, and 73 specimens of fossil geomyoids spanning the Oligocene through Pleistocene. Our initial results show a difference between the two families in the scaling of BF with size; for a given body size, geomyids have a consistently greater BF than heteromyids. We explored the link between BF and ecology by testing the hypothesis that chisel-tooth digging gophers have a greater BF than scratch-digging species. Our current analysis is limited to two species within the genus Thomomys: T. Monticola and T. Talpoides. We found no statistically significant difference between the BF of the two species. This could be a result of non-locomotory impacts on BF as well as evolutionary history. We also expected sexual dimorphism to have some impact on BF, but our results show instead that the BFQ of males and females are not significantly different in all but one species, the gopher Cratogeomys merriami. Our analysis of the fossil data shows that extant geomyids (subfamily Geomyinae) have a much higher BF than their fossil relatives (Entoptychinae), whereas fossil heteromyids include some species with higher bite forces than those observed in extant taxa. We are currently expanding our sampling and incorporating phylogenetic comparative methods into our study to explore this further.