Fossil Deer-like Ruminant Skull | Leptomeryx evansi | South Dakota

Leptomeryx evansi Oligocene Brule Formation White River Badlands Custer County, South Dakota   Specimen approx. size: 3.5" x 1.75" x 2.25" Stand not included.   Leptomeryx evansi is an extinct species of small artiodactyl (even-toed ungulate) that lived during the Eocene to early Oligocene epochs, approximately 40 to 30 million years ago, primarily in what is now North America. It belongs to the genus Leptomeryx, which is part of the family Leptomerycidae—a primitive and early offshoot of ruminant evolution.   Morphology Leptomeryx evansi was a diminutive, slender-limbed ungulate, about the size of a modern jackrabbit or small deer (roughly 5–10 kg in body mass). Its body was gracile, with long limbs adapted for swift, cursorial locomotion. Like other members of Leptomeryx, it had: Long metapodials (fused lower limb bones), indicating fast-running adaptations. Digitigrade posture, walking on its toes, much like modern deer. Small, simple cheek teeth, suggestive of a diet that included soft vegetation such as leaves and possibly fruits—characteristic of a browser. Skull features consistent with primitive ruminants, though it lacked some of the advanced dental and digestive adaptations seen in modern ruminants.   Paleoecology Leptomeryx evansi inhabited subtropical to temperate woodland and open forest environments. Its gracile form and browsing dentition suggest it foraged in areas with low to mid-level vegetation. It likely shared its habitat with other early ungulates, small perissodactyls (like early horses), and archaic carnivores.   Fossil Record Fossils of Leptomeryx evansi have been found in formations such as the White River Group (notably in South Dakota, Nebraska, and Wyoming). Specimens are typically represented by partial skeletons, limb bones, and jaw fragments with teeth.