tag="{http://www.w3.org/1999/xhtml}a">Genus *Grangerimus

514 Genus *Entoptychus 514 Subfamily Geomyinae 514 Tribe *Dikkomyini 515 Genus *Dikkomys 516 Genus *Pliosaccomys 517 Tribe Thomomyini 518 Genus Thomomys 518 Subgenus *Pleisothomomys 519 Subgenus Thomomys 520 Tribe Geomyini 521 Genus *Pliogeomys 522 Genus Zygogeomys 523 Genus Geomys 525 Genus Orthogeomys 528 Subgenus Orthogeomys 529 Subgenus Heterogeomys 530 Subgenus Macrogeomys 531 Genus Pappogeomys 532 Subgenus Pappogeomys 534 Subgenus Cratogeomys 535 Phylogeny of the Geomyidae 536 Primitive Morphotype 537 Entoptychid Radiation 540 Phyletic Trends in Subfamily Geomyinae 542 Plio-Pleistocene Radiation of Geomyini 558 Morphotype 559 Specializations in Genera 560 Zygogeomys 564 Geomys 565 Orthogeomys 568 Pappogeomys 569 Literature Cited 572

INTRODUCTION

When C. Hart Merriam wrote his monograph of the subfamily Geomyinae in 1895, he had no opportunity to examine fossil specimens. No doubt his phylogenetic conclusions and classification would have been greatly