Meeting Abstract
Entoptychine gophers are a species-rich and abundant group of rodents from the Oligo-Miocene of North America representing over 30% of some faunas. Yet, little is known about the paleoecology of these rodents, which are often represented by isolated craniodental remains. Material from the John Day Formation of Oregon and articulated skeletons from the Cabbage Patch beds of Montana allow a comprehensive study of the ecomorphology of these animals. Using a geometric morphometric framework built from extant rodent species, we analyze the skull shape of five entoptychine species. We compare the results to analyses of linear measurements of their postcranial skeletons. Analyses of skull morphology suggest that all three species of the genus Pleurolicus studied were terrestrial to semi-fossorial, with a morphology similar to that of some ground squirrels, voles, and lemmings. Both species of the younger, more derived, genus Entoptychus were classified as fossorial, but E. minor was likely less specialized than E. individens, which closely resembles extant geomyines. These results are congruent with analyses of postcranial data. The forelimb morphology of Pleurolicus indicates digging abilities similar to those of the extant chipmunks, suggesting terrestrial to semi-fossorial locomotion. The larger Entoptychus is characterized by hypertrophied forelimbs that suggest a semi-fossorial to fossorial locomotion. Combined with differences in body mass and incisor morphology across taxa, our results suggest that the evolution of fossoriality in entoptychines may have been linked to changes in diet and body mass through time.
