PTILODUS

extinct genus of mammals found as fossils in middle and late Paleocene deposits of North America (the Paleocene Epoch began 66.4 million years ago and lasted 8.6 million years). Ptilodus was a multituberculate, a group that once comprised the dominant herbivorous mammals of the Earth and in many respects was similar in function to the modern rodents. Ptilodus' teeth included long, rodentlike incisors, bladelike shearing teeth with striations, and molars with parallel rows of cusps. The palate had large vacuities, and powerful chewing muscles were attached to the lower jaw.