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Tylosteus

Pachycephalosaurus
Temporal range: Late Cretaceous, 70–66 Ma
Pachycephalosaurus wyomingensis dinosaur (Upper Cretaceous; Montana, USA).jpg
Cast of the "Sandy" specimen
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Order: Ornithischia
Family: Pachycephalosauridae
Tribe: Pachycephalosaurini
Genus: Pachycephalosaurus
Brown & Schlaikjer, 1943
(conserved name)
Type species
Pachycephalosaurus wyomingensis
Gilmore, 1931 (conserved name)
Species

Pachycephalosaurus wyomingensis
(Gilmore, 1931) (conserved name)

Synonyms

Tylosteus ornatus Leidy, 1872
(rejected name)

Troodon wyomingensis Gilmore, 1931
Stygimoloch spinifer? Galton & Sues, 1983
Dracorex hogwartsia? Bakker et al., 2006


Pachycephalosaurus wyomingensis
(Gilmore, 1931) (conserved name)

Tylosteus ornatus Leidy, 1872
(rejected name)

Troodon wyomingensis Gilmore, 1931
Stygimoloch spinifer? Galton & Sues, 1983
Dracorex hogwartsia? Bakker et al., 2006

Pachycephalosaurus (/ˌpækˌsɛfələˈsɔːrəs/; meaning "thick-headed lizard," from Greek pachys-/παχυς- "thick", kephale/κεφαλη "head" and sauros/σαυρος "lizard") is a genus of pachycephalosaurid dinosaurs. The type species, P. wyomingensis, is the only known species. It lived during the Late Cretaceous Period (Maastrichtian stage) of what is now North America. Remains have been excavated in Montana, South Dakota, and Wyoming. It was an herbivorous creature which is primarily known from a single skull and a few extremely thick skull roofs, though more complete fossils have been found in recent years. Pachycephalosaurus was one of the last non-avian dinosaurs before the Cretaceous–Paleogene extinction event. Another dinosaur, Tylosteus of western North America, has been synonymized with Pachycephalosaurus.


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