Abstract

Entoptychine gophers are a species-rich subfamily of the Geomyidae from the Oligo-Miocene known from countless teeth, numerous jaws, and rare skulls and skeletons. Because of this rich fossil record, entoptychine gophers have greatly contributed to our understanding of the biostratigraphy, biogeography, and paleoecology of fossil deposits of the western United States. Nonetheless, there is currently no phylogenetic framework for the subfamily. We describe four new species of entoptychines from the Arikareean-aged Cabbage Patch beds of Montana, including three species of the genus Pleurolicus (P. gwinni, P. nelsoni, and P. rensbergeri) and one species of Gregorymys (G. tavenneri) and include these taxa into the first phylogenetic analysis of Entoptychinae to include all species within Pleurolicus Cope, 1878, Gregorymys Wood, 1936, and Ziamys Gawne, 1975, as well as a species of the genus Entoptychus Cope, 1878. We recover a paraphyletic Pleurolicus at the base of the tree. Ziamys is a monophyletic genus, sister taxon to the clade formed by the genera Entoptychus and Gregorymys. Within Pleurolicus, the species strictly from the Great Plains form a clade. Gregorymys is divided into two major clades, one that includes the southern species G. riograndensis Stevens, 1977, and G. veloxikua Jiménez-Hidalgo et al., 2018, as well as G. riggsi Wood, 1936, and G. tavenneri and one including all other species from the northern Great Plains and Rocky Mountains. Gregorymys kayi Wood, 1950, a poorly known outlier species of the genus is sister to the Entoptychus species included in our analysis. Our findings suggest a complicated evolutionary history for the Entoptychinae, but also offer the opportunity for fruitful future analyses of evolutionary ecology.