Gregorymys veloxikua, The Oldest Pocket Gopher (Rodentia: Geomyidae), and The Early Diversification of Geomyoidea

Abstract

The rodent family Geomyidae is native to America. It comprises six extant genera with 40 species distributed from Saskatchewan, Canada to northern Colombia. Two subfamilies are included in the family, the extinct Entoptychinae, with a fossil record ranging from the late Oligocene (Arikareean) to the middle Miocene (Barstovian) and the Geomyinae, with a chronological range from middle Miocene (Barstovian) to Recent. Here, we describe a new species of Gregorymys, G. veloxikua, the oldest known entoptychinae, from the late Eocene fluviolacustrine sediments of Santiago Yolomécatl, Oaxaca, Mexico. The record of this geomyid in southern Mexico suggests that the early diversification of superfamily Geomyoidea began earlier than the late Eocene in southern Mexico/Central America. The direct association of several studied specimens with burrows indicates that fossoriality was acquired early in the evolution of the family.