Using 2D dental geometric morphometrics to identify modern Perognathus and Chaetodipus specimens (Rodentia, Heteromyidae)

The Heteromyidae (pocket mice and kangaroo rats) are a group of extant small rodents abundant in western North America, as well as in fossil assemblages over the last 20 million years. Two genera of heteromyids, Chaetodipus and Perognathus, share similar tooth morphology and teeth are the primary fossil remains. Previous genetic studies show these extant sister genera likely diverged in the middle Miocene (∼16 million years ago); however, the Chaetodipus fossil record starts in the Pleistocene (∼2 million years ago). In this study, we asked whether two-dimensional geometric morphometrics on complete dentition and isolated premolars can accurately identify Chaetodipus and Perognathus specimens at the genus and species level. We landmarked the occlusal surface of the upper and lower tooth rows of modern Chaetodipus (n = 83) and Perognathus specimens (n = 80), including 12 of the 26 extant species across the two genera. We ran a canonical variates analysis to investigate whether principal component variation could predict known taxonomic identifications. The morphospace using complete dentition can identify specimens to genus with 90 – 92% accuracy and to species with more variable accuracy. We found an isolated premolar provides sufficient information for genus-level identification (69 – 84% accuracy), but not for species-level identification (26 – 56% accuracy). This morphospace of modern specimens can be used to identify the skeletal remains of Chaetodipus and Perognathus in museum collections, raptor pellets, or middens, to refine our existing knowledge of heteromyid evolutionary history.