Heteromyidae

Abstract

With only a few exceptions in the fossil record, heteromyids (pocket mice and kangaroo rats) are small animals. Their skulls are generally delicate in construction (Fig. 16.1) with thin, delicate zygoma and are fully sciuromorphous. The infraorbital foramen is dorsal to the center of the diastema and positioned just ventral to middepth of the rostrum opening laterally. Continuous with the infraorbital foramen is a large rostral perforation not present in any other rodents. As with all geomyoid rodents, there is a distinct parapterygoid fossa on the palate. The attachment of the temporalis muscle is restricted to the lateral sides of the parietal bones, producing no well-defined sagittal or lyrate crests. The rostrum is generally tapered anteriorly. Dorsally, the premaxillary bones extend farther posteriorly than the nasals on the skull roof.