Origin and Evolutionary Relationships among Geomyoids

Abstract

Contents, relationships, and origin of geomyoid rodents have been commented on quite differently during the past, in zoology as well as in paleontology. On the part of zoologists this superfamily contains the well defined families Heteromyidae and Geomyidae, both of them restricted more or less to North America. According to jaw musculature they are mostly assigned to the Sciuromorpha. Following Wilson’s (1949) revision of some Oligocene Eomyidae, these also were incorporated into the Geomyoidea by many paleontologists. Moreover, as Wilson (1949) discussed morphological relations to some myomorphs (in which, however, he did not put them), the whole superfamily later became attributed to the Myomorpha in paleontological literature (e.g. Wood, 1955a), a fact, I believe, with which zoologists became scarcely familiar. Some people even considered the whole group to be a separate suborder Geomorpha (Thaler, 1966). Due to the lack of adequate fossils, little is known of the origin of these rodents, except for some necessarily preliminary assumptions dealing with various groups of the Protrogomorpha as possible ancestors.