| Pachycephalosaurs Temporal range: Late Cretaceous, 90–66 Ma |
|
|---|---|
| Cast of a Pachycephalosaurus wyomingensis skull, Oxford University Museum of Natural History | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Order: | †Ornithischia |
| Suborder: |
†Pachycephalosauria Maryańska & Osmólska, 1974 |
| Family: |
†Pachycephalosauridae Sternberg, 1945 (conserved name) |
| Type species | |
|
†Troodon wyomingensis Gilmore, 1931 (conserved name) |
|
| Genera | |
| Synonyms | |
|
Homalocephalidae Dong, 1978 |
|
Homalocephalidae Dong, 1978
Pachycephalosauria (/ˌpækiˌsɛfələˈsɔːriə, ˌkɛ-/; from Greek παχυκεφαλόσαυρος for 'thick headed lizards') is a clade of ornithischian dinosaurs. Genera include Pachycephalosaurus, Stegoceras, and Prenocephale. Most lived during the Late Cretaceous Period, in what is now North America and Asia. They were all bipedal, herbivorous/omnivorous animals with thick skulls. In some fossils, the skull roof is domed and several centimeters thick; in others it is flat or wedge-shaped. While the flat-headed pachycephalosaurs are traditionally regarded as distinct species or even families, they may represent juveniles of dome-headed adults. The domes were often surrounded by nodes and/or spikes.