Wannanosaurus

thumb|Life reconstruction|left Wannanosaurus (meaning "Wannan lizard", named after the location where it was discovered) is a genus of basal pachycephalosaurian dinosaur from the Maastrichtian-aged (Upper Cretaceous) Xiaoyan Formation, about 70 million years ago, in what is now Anhui, China. The type species Wannanosaurus yansiensis was described by Hou Lian-Hai in 1977.

It is known from a single partial skeleton, including a partial skull roof and lower jaw, a femur and tibia, part of a rib, and other fragments. Because it has a flat skull roof with large openings, it has been considered primitive among pachycephalosaurs. Sometimes it has been classified as a member of the now-deprecated family Homalocephalidae, now thought to be an unnatural assembly of pachycephalosaurs without domed skulls. Although its remains are from a very small individual, with a femur length of approximately and an estimated overall length of about , the fused bones in its skull suggest that it was an adult at death. Like other pachycephalosaurs, it was probably herbivorous or omnivorous, feeding close to the ground on a variety of plant matter, and possibly insects as well.