Revision of the Miocene and Pliocene Equidae of North America. Bulletin of the AMNH ; v. 23, article 35.

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New York : Published by order of the Trustees, American Museum of Natural History
"In the foregoing revision the lines of comparison and study have been confined principally to characters of the teeth and skull, for the reason that by far the greater number of species of horses have been founded on tooth and skull material not associated with other parts of the skeleton. The expeditions of the last few years however are constantly increasing the collections and adding quantities of more complete material, including many specimens in which teeth and bones of the feet are associated. This class of material will greatly aid in working out more fully than has been done the characters of foot development of horses, and should result in throwing added light on the phyletic relations of the extremely varied groups which seem to have reached their culmination, as regards numbers of genera and species, in the Miocene period. The principal results attained by this study are, first, a better understanding and interpretation of the principal characters shown in the numerous and varied types representing the American Miocene horses; second, the reestablishment and better definition of several of the genera and species proposed by Leidy, the validity of which was questioned by Cope; and third, a reclassification of the entire family of the Equiidae. As at present understood, the fact seems to be fairly well established that there is a considerable phyletic hiatus between the groups of the Equidae as above subdivided, which are as yet not bridged over by intermediate forms. Such a hiatus seems especially marked between the Anchitheriinae and the Protohippinae, while these groups greatly overlap each other in time. So far as indicated by any known species the Anchitheriinae could not well have stood in direct ancestral line to the latter group or to the Equiinae. There seems also to be almost as decided a gap between the Anchitheriinae and the known species of the older group, the Hyracotheriinae. The Equiinae may well have been derived from some species of the Protohippus division of the Protohippinae"--P.933-934.
p. 865-934 : 1 ill. ; 24 cm.
Includes bibliographical references.