Evolution and Classification of the Pocket Gophers of the Subfamily Geomyinae

Evolution and Classification of the Pocket Gophers of the Subfamily Geomyinae

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 influenced had he enjoyed that opportunity because study of fossil geomyids reveals the historic sequence of phyletic development, and this sequence provides a firm basis for distinguishing specialized from primitive characters. The history of the Geomyinae has been characterized by the evolution of specializations. These evolutionary trends begin, as we presently know them, with a generalized ancestral stock in the early Miocene. The direction, degree, and rate of change, beginning with the primitive morphotype of the subfamily, has not been the same in the various lineages. The classification within the subfamily is based upon the phyletic interpretations of available data and the relationships they disclose. In turn, a new, and I hope more realistic, phylogeny and classification is offered. Recent specimens were studied of all the known genera, subgenera and 29 of the 36 living species. Most of the species not studied are monotypic and have restricted geographic ranges. They are: Geomys colonus, G. fontanelus, and G. cumberlandius, Orthogeomys cuniculus and O. pygacanthus of the subgenus Orthogeomys, and O. dariensis and O. matagalpae of the subgenus Macrogeomys. Examination of these modern species would not radically change the estimation of the degree of phyletic development of the genera and subgenera involved. All of the major polytypic and widespread species were studied. ......Buy Now (To Read More)

Product details

Ebook Number: 40282
Author: Russell, Robert J.
Release Date: Jul 20, 2012
Format: eBook
Language: English