Pachycephalosaurs Temporal range: Late Cretaceous, 90–66 Ma |
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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) |
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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 actually represent juveniles of dome-headed adults. The domes were often surrounded by nodes and/or spikes.