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Early Tertiary Rodents of North America

Wilson, Robert W. (1949) Early Tertiary Rodents of North America. In: Some Tertiary Mammals and Birds from North America. Carnegie Institution of Washington Publication. No.584. Carnegie Institution of Washington , Washington, DC, pp. 67-164.

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The gnawing mammals of the present day exist in the greatest of profusion and diversity. In sheer population they exceed all other mammals combined, and this is nearly as true of number of species and genera. In the higher taxonomic categories below the rank of suborder, their great diversity is shown by the much greater number of families and subfamilies than in any other order of mammals. Almost all these gnawing animals are classified in a single order, the Rodentia (rodents). Those that are not, the Lagomorpha (hares, rabbits, pikas), though existing in considerable numbers, are among the most homogeneous of orders. They are at best only distantly related to the rodents. The following remarks apply only to the Rodentia. The great number of categories necessary for classifying existing rodents testifies to the tremendous evolutionary development which has taken place within the order. A second outstanding feature of the order is the astonishing amount of parallelism in tooth pattern between forms placed in different major groups. The same pattern in some instances is reproduced several times over. The repeated parallel developments in both living and fossil rodents suggest that all these animals have descended from a common ancestor which lived in the not too remote past. It is generally agreed that the greater the parallelism, the greater the genetic relationship, and this tenet applies not only to duplication of pattern, but necessarily also in some measure to the number of such duplications. Similar needs acting on distantly related groups should not be so effective in producing parallelisms as are those which act on closely related stocks.

Item Type:Book Section
Additional Information:© 1949 Carnegie Institution of Washington. This paper has been prepared during the author's tenure as National Research Council Fellow in paleontology, 1946-1947. I wish to thank the National Research Fellowship Board in the Natural Sciences for making this work possible. Also my thanks are due to the Division of the Geological Sciences, California Institute of Technology, for research facilities, and particularly to Dr. Chester Stock, of the California Institute, for sponsoring the project through a number of years, and for a critical reading of the manuscript. Because this work is based on a program of study and systematic description over a number of years, it is appropriate at this time to express my thanks again to Yale University for appointment as Sterling Research Fellow, 1936-1937; and to Mr. Childs Frick for financial assistance during the period 1937-1939, at which time I was Research Fellow in paleontology at the California Institute of Technology. The text figures have been prepared by Mr. David P. Willoughby, scientific illustrator, Division of the Geological Sciences, California Institute of Technology.
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National Research CouncilUNSPECIFIED
Yale UniversityUNSPECIFIED
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Balch Graduate School of the Geological Sciences408
Series Name:Carnegie Institution of Washington Publication
Issue or Number:584
Record Number:CaltechAUTHORS:20211220-185607784
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112557
Deposited By: Tony Diaz
Deposited On:20 Dec 2021 23:10
Last Modified:20 Dec 2021 23:10

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