Temporal range: Late Cretaceous
An artist's illustration of Pachycephalosaurs wyomingensis
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Order: Ornithischia
Family: Pachycephalosauridae
Tribe: Pachycephalosaurini
Genus: Pachycephalosaurus
Brown & Schlaikjer, 1943
Species: P. wyomingensis
Binomial name
Pachycephalosaurs wyomingensis
Gilmore, 1931

Pachycephalosaurus/Tylosteus is a genus of pachycephalosaurid dinosaurs. It lived during the late cretaceous in what is now North America. Remains have been excavated in Montana. It was an herbivorous creature which is only known from a single skull and a few extremely thick skull roofs. Pachycephalosaurus lived 68-67 mya.


Pachycephalosaurus skull

A cast of the only Pachycephalosaurus skull

Pachycephalosaurus was probably bipedal and was the largest known of the bone-headed dinosaurs, with some others being Stygimoloch, Dracorex, and Stegoceras. It is famous for having a large, bony dome atop its skull, up to 25 cm (10 inches) thick, which safely cushioned its brain. The dome's rear aspect was edged with bony knobs and short bony spikes were projected upwards from the snout. These features suggest that, despite their bipedal stance, they were likely to have been relatives of the ceratopsians.

Using data from other pachycephalosauridae, it has been estimated that Pachycephalosaurus was approximately the length of a large car, maybe around 4.6m long (15 feet) and had a fairly short, thick neck, short fore limbs, a bulky body, long hind legs and a heavy tail, which was likely to have been held rigid by ossified tendons. Large eye-sockets that faced forward suggest that the animal had good vision and was capable of binocular vision.

Pachycephalosaurus scale

Estimated scale between a Pachycephalosaurus adult and a human


Scientists once suspected that Pachycephalosaurus and its dome-headed relatives were the bipedal equivalents of the big-horned sheep of today. It was thought that, in the mating season, big males would run at one another, clashing heads to decide which would dominate and mate with a herd of females. It was also thought that they might have used their domed heads for defence against predators. However, it is now believed that the Pachycephalosaurs would not have used their domes in this way so much. The adult head bones could not adequately have withstood pressure and impact and the skulls lacked proper shock absorption like Big Horned Sheep, and it's more likely that they head-butted their sides, to try to knock them off balance. Also, there is no evidence of scars or other damage on fossilized Pachycephalosaurus skulls. On the other hand, it's unlikely that pachycephalosaurs developed those thick skulls for display alone. It's a rather opinionated discussion.
Pachycephalosaurus skull

Adult skull in two perspectives

Scientists do not yet know what these dinosaurs ate. Having very small, ridged teeth they could not have chewed tough, fibrous plants as effectively as other dinosaurs of the same period. It is assumed that pachycephalosaurs lived on a mixed diet of leaves, seeds, fruit and insects. The sharp, serrated teeth would have been very effective for shredding plants.

In The Media

  • Pachycephalosaurus appeared in the 1997 film The Lost World: Jurassic Park stampeding with the other dinosaurs. One of them appeared in the 2015 film Jurassic World & was tranquilized to sleep after escaping it's enclosure. While not in the trailers so far for the 2018 Jurassic World: Fallen Kingdom, it has been revealed that there are surviving Pachycephalosaurus populations on Isla Nublar, but they and many other dinosaurs will now face an impending danger in the form of an erupting volcano.

    The Lost World: Jurassic Park Pachycephalosaurus

  • Pachycephalosaurus also had some roles in the Land Before Time franchise, where they are depicted as secondary villains. A trio of Pachycephalosaurus attack Cera in The Land Before Time, but they make their return in The Land Before Time IV: Journey Through the Mists when a pair of them fight each each and Petrie gets dizzy to see them fighting. However in the later movies they were one of the dinosaurs living in the Great Valley.
  • Pachycephalosaurus appeared in the 35th episode of Dink, the Little Dinosaur & one of them was a new but minor character & Allie named Nobbie.
  • Pachycephalosaurus made some appearances in DinoRiders.
  • A Dinosaucer Pachycephalosaurus named Bonehead appears in Various episodes of Dinosaucers, Bonehead can sometimes Devolve into his ancestral appearance.
  • Pachycephalosaurus made some appearances in Cadillacs & Dinosaurs. "Both Some Comic Books & only episode 12 nicknamed a bonehead".
  • Some Pachycephalosaurus appeared in a few episodes of Kong: The Animated Series. One of them was also seen briefly on the Film Kong Return to the Jungle.
  • Pachycephalosaurus is the title of a song on a 2006 album by the band Showbread, entitled Age of Reptiles. However, despite its name, the song itself doesn't have something to do with the dinosaur.
  • The Transforme

    Primeval: New World Pachycephalosaurus

    rs characters of Hardhead and Dinotron turned into Pachycephalosaurus.
  • A Zord in Power Rangers: Dino Thunder was based on Pachycephalosaurus, and another in Power Rangers: Dino Charge.
  • Pachycephalosaurus made a few appearances in the video game Jurassic The Hunted. "Both dead & alive. The PS2 version featured only the living Pachys Stampeding to get away from Spike the Spinosaurus.
  • Pachycephalosaurus was featured in a PS3 Game Wonderbook: Walking With Dinosaurs. Staring The 2 Notable individuals Ficus & Lily in the 2 part Final Chapter Level King of Dragons.
  • Pachycephalosaurus also appeared in a couple Dinosaur Arcade Games The Lost World Jurassic Park & Savage Quest.
  • It is a huntable species in Carnivores.
  • A juvenile Pachycephalosaurus is seen chased by two Juvenile T.Rexes & another hunted by a pair of Troodon in Dinosaur Revolution (Dinotasia). It is the model of the scrapped Prenocephale.
    Jurassic world pachycephalosaurus by sideswipe217-d8qhkv9

    Jurassic World Pachycephalosaurus

  • Pachycephalosaurus appears in Two National Geographic Documentaries Bizarre Dinosaurs & in Dinosaurs Decoded, where Jack Horner talks about how Stygimoloch and Dracorex are actually young Pachycephalosaurus, however, not many people agree with this, and the idea has mostly been rid of.
  • It also appeared in Dinosaur Train in season 2. Featuring the 2 Siblings Patrick & Pamela Pachycephalosaurus in the Episode Dome Headed Dinosaur.
  • Pachycephalosaurus will be in the upcoming game Saurian as a playable dinosaur.
  • In Dinozaurs There's a character named Dino Pachy his dinosaur form is a Pachycephalosaurus and his Dino Weapon mode is the Pachy Spike Sword.
  • A Pachycephalosaurus appeared in a few episodes of Dinosaur King. It was also one of the Secret Dinosaurs with tremendous powers.
  • In Pokemon series, Cranidos and its evolved form Rampardos are based on Pachycephalosaurus. These two Pokemon were first introduced in the video games, Pokemon Diamond & Pearl.
  • Pachycephalosaurus appears in Anime film Age of the Great Dinosaurs with one being the victim of the one-eyed Tyrannosaurus rex.
  • It was also in the 1994 Japanese film Tyranno's Claw.
  • The Pachycephalosaurus is one of the many creatures you can tame in the survival game Ark: Survival Evolved