Master's Theses

Department

Geosciences

Degree Name

Master of Science (MS)

Abstract

Populations of fossil wood rats (Neotoma) from four geographically separated sites (Cumberland Cave, Conrad Fissure, Java, and Vallecito Creek: of presumed Irvingtonian age and eight species of extant wood rats were studies to determine interrelationships. Four measurements and three ratios, calculated from the measurements were taken on molars from the four populations. The same measurements were made on eight species of extant wood rats to serve as a reference. Discriminant analyses reveal that isolated molars cannot be used to separate wood rats into subgenera and species. However, successful separation of wood rats into subgenera and species can be achieved by using one side of both the upper and lower tooth rows (a total of six molars). A combination of fourteen variables, such as the length of M1, can be used to separate the extant species, whereas fifteen variables can be used to separate the extant subgenera. Because it is impossible to assign isolated fossil molars to an individual wood rat, hypothetical individuals were made from the fossil material to facilitate comparisons to the extant material. Seventeen variables such as the length of M1, can separate the fossil populations. The use of hypothetical individuals for the fossils was justified from the results obtained from the extant individuals by constructing a control group of hypothetical individuals form those already analyzed. The extant hypothetical individuals were a composite of six different wood rats. Analytical results of the extant hypothetical individuals were found to be in agreement with the results of the true individuals. Analyses show that extant wood rats have a majority of characteristic measurements (9of 14, species; 9 of 14, subgenera) associated with the lower molars, whereas fossil wood rats have the majority of characteristic measurements (10 of 17) associated with the upper molars. Evidence for a generic status for Hodomys and Parahodomys and a subgeneric status for the specimens from Conrad Fissure and Vallecito Creek is demonstrated.

Advisor

Richard Zawerksi

Date of Award

Summer 1982

Document Type

Thesis - campus only access

Rights

© 1982 Joseph J. Folwarczny

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