Evolution and Classification of the Pocket Gophers of the Subfamily Geomyinae

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Gutenberg ID

40282

Title

Evolution and Classification of the Pocket Gophers of the Subfamily Geomyinae

Language

en

Book source

Project Gutenberg

Description max 80 words

Robert J. Russell presents a definitive taxonomic study of pocket gophers, tracing their evolutionary history from early Miocene ancestors to modern species. This scholarly work details morphological specializations in teeth and skulls, offering a realistic phylogeny based on fossil and living specimens.

Summary up to 500 words

In his 1968 monograph, *Evolution and Classification of the Pocket Gophers of the Subfamily Geomyinae*, Robert J. Russell presents a comprehensive revision of pocket gopher taxonomy, integrating fossil records with modern specimens to construct a robust phylogeny. Russell argues that classification based solely on living forms is insufficient; instead, he utilizes the historic sequence of development revealed by paleontology to distinguish primitive traits from derived specializations. The study examines extinct genera such as *Entoptychus* and *Dikkomys* alongside living tribes like Thomomyini and Geomyini. Russell systematically analyzes key morphological characters driving evolutionary trends. A primary focus is the prismatic evolution of molars, which transitioned from a primitive bicolumnar pattern to a specialized monocolumnar structure. Concurrently, he tracks the reduction of enamel loops and the development of incisor grooves adapted for fibrous diets. Structural changes in the lower jaw, including the elaboration of the masseteric ridge and basitemporal fossa, are linked to increased masticatory power. The text highlights parallel evolution between *Geomys* and *Zygogeomys*, while noting unique adaptations in *Orthogeomys* and *Pappogeomys*. The work details specific dental patterns, such as the shift from bilophate to single-loph enamel patterns and the interruption of enamel bands by dentine tracts. It also explores the functional significance of incisor grooving, suggesting these serrated edges aid in cutting fibrous roots. By grounding his classification in the temporal sequence of these changes, Russell offers a realistic system that corrects earlier misconceptions, providing a firm basis for understanding the phyletic trends of the Geomyinae from the early Miocene to the Recent.

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• Science