A new omomyid primate from the Wasatch formation of southern Wyoming.

A new omomyid primate, Arapahovius gazini, is represented by many jaws and teeth and a few tarsal bones from a 15-meter stratigraphic interval at the base of the uppermost one-third of the Main Body of the Wasatch Formation, south-central Wyoming, USA. This primate is a conspicuous element in a faunule which lived at about the same time as the fauna of the Lysite Member of the Wind River Formation, estimated to be in the interval 52-50 million years before present. Individuals referable to the new omomyid are chiefly specialized by the intricate corrugation of enamel on the occlusal surfaces of their incisors, premolars and molars and by relatively molariform posterior lower premolars. These specializations may be interpreted as adaptation toward a more herbivorous-frugivorous diet. The tarsal bones referred to Arapahovius suggest that animals in this genus were habitual leapers. This new omomyid bears 'omomyine' and 'anaptomorphine' characters and may have been derived from an earlier Wasatchian (earliest Eocene) 'anaptomorphine' such as Tetonoides pearcei Gazin. Arapahovius seems to have had no phylogenetic successors.