Kingdom Animalia
Phylum Chordata
Superclass Tetrapoda
Class Reptilia
Subclass Diapsida
Superorder Dinosauria
Order Ornithischia
Suborder Pachycephalosauria
Family Pachycephalosauridae
Subfamily Pachycephalosaurinae
Genus Pachycephalosaurus
1st Species Pachycephalosaurus wyomingensis
2nd Species Pachycephalosaurus spinifer
Other attributes
Time Range 70-66 mya
Location United States of America
Name Meaning Thick-headed reptile
Physical Dimensions 5 meters long
Weight 450 kilograms
Dietary Classification Omnivore

Pachycephalosaurus is a pachycephalosaurid pachycephalosaurian marginocephalian dinosaur from the Late Cretaceous of the United States of America. It was named in 1931 by Charles W. Gilmore. Unlike other popular prehistoric animals, it is known from fragmentary remains, and so, is modeled off of similar, more complete relatives; this is also the case with two other dinosaurs, Spinosaurus and Ankylosaurus.


Pachycephalosaurus was a bipedal marginocephalian with a broad body, long legs, a long, slender tail, short arms, and a small beak in the front of its mouth. Its most notable feature is the large, bony, spiky dome atop its forehead, hence the meaning of its name, "thick-headed lizard". Its body would have been covered in scaly skin.


Pachycephalosaurus would have been an omnivore, feeding on leaves, seeds, fruits, and insects. Having small, ridged teeth, it would have shredded leaves rather than chewing tough, fibrous plants.


Pachycephalosaurus's bony head dome was used as a weapon against predators like juvenile Tyrannosaurus, as well as rival males during mating season. It has long been suspected that Pachycephalosaurus would charge at each other at full speed and butt heads; however, this was disproved, as the structure of their head domes were partially filled with spongy bone marrow rather than completely solid bone, and would crumble when hit successively. As well as this, it held its neck in a curved orientation, making it unfit for direct head combat. Instead, rival male Pachycephalosaurus would have either circled each other and butt heads, or hit each other in the sides of their bodies with their heads.

In popular cultureEdit

Pachycephalosaurus was first introduced to the public in the 1988 movie, The Land Before Time, where it was depicted as a rather territorial brute. Since then, it has appeared in major pieces of media like Jurassic Park and Primeval.

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