The distinctive dome-headed Pachycephalosaurus is believed to have used its thick skull during combat with others of its species, perhaps while trying to impress potential mates. They may have butted their heads together or slammed them into each other's sides. This detailed Pachycephalosaurus figure will transport you back to the Late Cretaceous Period! History: Pachycephalosaurus was formally discovered and named in 1931, though some fossil material may have been found much earlier. It is known only from skulls, and its body design is based on more completely known relatives including Stegoceras. It is believed that two similar pachycephalosaurs Dracorex and Stygimoloch may actually represent different growth stages of Pachycephalosaurus. This theory suggests that as the dinosaur grew, the spikes on its head became blunter, and the dome on top of its skull became more pronounced. Scientific Name: Pachycephalosaurus (thick-headed lizard)