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''Pachycephalosaurus'' (; 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 or omnivorous 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''. Like other pachycephalosaurids, ''Pachycephalosaurus'' was a bipedal omnivore with an extremely thick skull roof. It possessed long hindlimbs and small forelimbs. ''Pachycephalosaurus'' is the largest known pachycephalosaur. The thick skull domes of ''Pachycephalosaurus'' and related genera gave rise to the hypothesis that pachycephalosaurs used their skulls in intra-species combat. This hypothesis has been disputed in recent years. ==Description== The anatomy of ''Pachycephalosaurus'' is poorly known, as only skull remains have been described. ''Pachycephalosaurus'' is famous for having a large, bony dome atop its skull, up to 25 cm (10 in) thick, which safely cushioned its tiny brain. The dome's rear aspect was edged with bony knobs and short bony spikes projected upwards from the snout. The spikes were probably blunt, not sharp. The skull was short, and possessed large, rounded eye sockets that faced forward, suggesting that the animal had good vision and was capable of binocular vision. ''Pachycephalosaurus'' had a small muzzle which ended in a pointed beak. The teeth were tiny, with leaf-shaped crowns. The head was supported by an "S"- or "U"-shaped neck.〔 ''Pachycephalosaurus'' was probably bipedal and was the largest of the pachycephalosaurid (bone-headed) dinosaurs. It has been estimated that ''Pachycephalosaurus'' was around long and weighed . Based on other pachycephalosaurids, it probably had a fairly short, thick neck, short fore limbs, a bulky body, long hind legs and a heavy tail, which was likely held rigid by ossified tendons. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pachycephalosaurus」の詳細全文を読む スポンサード リンク
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