30-Million-Year-Old Canid Reveals Tree-Climbing Ancestor, Not a Runner

A nearly complete 30-million-year-old canid fossil from Oregon, Mesocyon coryphaeus, shows an animal built for climbing rather than running, with a rotatable elbow and a large dewclaw; the skeleton is among the most complete pre-Ice Age canids in North America and indicates this early dog sometimes climbed and grappled, not sprinting like modern dogs, and was identified as male by the preserved baculum. The discovery—initially misidentified as an oreodont—highlights how extinction erased a distinct early dog ecology that has no exact modern replacement.