The first Eocene vertebrate assemblage known from the Great Basin, the Elderberry Canyon Local Fauna, occurs in rocks referred to the Sheep Pass Formation near Ely, Nevada. Approximately 40 taxa are now known, including small anuran amphibians, small reptiles, birds, and mammals. The mammalian component consists of: the insectivorans Apatemys bellus, Pantolestes longicaudus, a tiny apternodont, at least one nyctitheriid, and at least four other taxa representing dormaalid and/or erinaceid erinaceomorphs; an epoicotheriid palaeanodont, cf. Tetrapassalus mckennai; the primates Notharctus tenebrosus, Trogolemur myodes, and two species of uintasoricines; the rodents Reithroparamys delicatissimus, R. cf. R. huerfanensis, Sciuravus sp., Microparamys sp., Pauromys sp., Mattimys sp., and two new genera; the hyaenodont Sinopa minor; two viverravid carnivores including Viverravus; the condylarth Hyopsodus paulus; the perissodactyls Hyrachyus modestus, Hyrachyus affinis, Helaletes nanus, Isectolophus latidens, and a new genus and species; and the artiodactyl Antiacodon pygmaeus.

Greatest faunal similarity is with the Black’s Fork Member (or lower), Bridger Formation, and other early Bridgerian localities such as Powder Wash in the Douglas Creek Member of the Green River Formation in northeastern Utah. The age of the Elderberry Canyon Local Fauna can confidently be called early Bridgerian.

The Elderberry Canyon Fauna is preserved in carbonate rocks believed to have been deposited in a shallow, warm, heavily vegetated, permanent, hardwater lake. The mammals lived on marshy wetland terrain adjacent to the lake, although some faunal elements may have been transported in from more distant habitats.