A new species of cf. Dilophodon (Mammalia; Perissodactyla) from the early Bridgerian of southwestern Wyoming

Abstract

ABSTRACT A new species of the diminutive ceratomorph similar to Dilophodon is reported from the latest early Eocene at Desertion Point in the Little Muddy area, Green River Basin, Wyoming. The Little Muddy specimens are assigned to cf. Dilophodon on the basis of their small size, simple premolars, absence of a first lower premolar resulting in a long post-canine diastema, and absence of a hypoconulid on the m3. Cf. Dilophodon destitutus, sp. nov. is the only helaletid known from the latest Early Eocene of the southwestern Green River Basin. It is considerably smaller than other species of Dilophodon. Its premolars are longer and narrower than in Dilophodon leotanus. The lophids on the lower molars are simpler and less posteriorly deflected than in either D. leotanus or Dilophodon minusculus. Dilophodon was previously known only from the middle Eocene (“Bridger C,” Bridgerian zone Br3) of southwestern Wyoming, and the late Eocene (Uintan, zone Ui3) of Wyoming, northern Utah, Montana, and possibly California. The specimens described here extend the chronologic range of Dilophodon to include the latest early Eocene (lower “Bridger A”; Bridgerian zone Brlb) of the Green River Basin, southwestern Wyoming.