The Eocene Mammals from the Lysite Member, Wind River Formation of Wyoming

Revision of the mammals from the type area of the lower Eocene Lysite is possible on the basis of three collections in the Amherst Museum. Additions to the known fauna include the rodent, Leptotomus; the creodonts Thryptacodon, Anacodon and Prolimnocyon; the uintathere, Probathyopsis; the pantodont, Coryphodon; and the artiodactyl, Diacodexis. Sufficient material is at hand to permit a statistical analysis of two genera, Hyopsodus and Hyracotherium, which shows that the morphologic characters heretofore used to characterize species are generally individual variants, and that not more than three species of Hyopsodus and two of Hyracotherium are present. Two new species are described: Thryptacodon loisi and Probathyopsis lysitensis.