Phenacodus (Greek for "obvious teeth"); pronounced fee-NACK-oh-duss
Plains of North America
Early-Middle Eocene (55-45 million years ago)
Size and Weight:
About 5 feet long and 50-75 pounds
Long, straight legs; long tail; narrow snout
Phenacodus was one of the "plain vanilla" mammals of the early Eocene epoch, a medium-sized, vaguely deer- or horse-like herbivore that evolved a mere 10 million years after the dinosaurs had gone extinct. Its importance lies in the fact that it seems to have occupied the root of the ungulate family tree; Phenaocodus (or a close relative) may have been the hoofed mammal from which later perissodactyls (odd-toed ungulates) and artiodactyls (even-toed ungulates) both evolved. This creature's name, Greek for "obvious teeth," derives from its, well, obvious teeth, which were well-suited to grinding up the tough vegetation of its North American habitat.