Helaletes Heptodon Tapiroidea List of the Cenozoic life of Nevada List of the Cenozoic life of Utah List of the prehistoric life of Nevada List of the prehistoric life of Utah List of the Cenozoic life of Montana List of the prehistoric life of Colorado List of the prehistoric life of Montana List of the prehistoric life of Wyoming List of the Cenozoic life of Wyoming Wasatch Formation Perissodactyla List of the Cenozoic life of Colorado Helaletidae Washakie Formation Bridger Formation