Pachycephalosauridae is a family within the order Pachycephalosauria, comprising dinosaurs famous for their thick, domed skulls. These “bone-headed” dinosaurs were primarily bipedal herbivores or omnivores, and their fossil remains have been found mainly in Late Cretaceous sediments in North America and Asia.
- Belong to the larger group Pachycephalosauria, known for thickened skulls.
- Lived during the Late Cretaceous period (~100 to 66 million years ago).
- Fossils mostly from North America and Asia.
- Known for unique dome-shaped or ornamented skulls, possibly used in head-butting or display.
Late Cretaceous
Pachycephalosaurid fossils are mainly found in North America and Asia.
Their thickened, domed skull roofs are a distinctive feature.
1. Pachycephalosaurus
Pachycephalosaurus is the most famous genus in Pachycephalosauridae, known for having some of the thickest skull domes among dinosaurs, sometimes exceeding 25 cm in thickness. They lived in North America during the Late Cretaceous (about 76-66 million years ago) and could grow up to 4.5 meters long. Fossil evidence suggests they used their domed skulls for intraspecific combat or display.
- Lived: Late Cretaceous (≃76–66 Ma)
- Region: North America
- Skull dome: Up to 25 cm thick
- Length: Up to 4.5 meters
Their thick skull was likely used for head-butting during intraspecific combat or for display.
Pachycephalosaurus lived during the Cretaceous period.
A thick, domed skull
Late Cretaceous
*Pachycephalosaurus* fossils have been found in North America.
2. Stegoceras
Stegoceras was a smaller pachycephalosaurid, about 2 meters long, and is known for its thick, dome-shaped skull as well as prominent bony knobs and spikes along the rear of the skull. It lived in North America during the Late Cretaceous (roughly 76-69 million years ago).
- Length: ~2 meters
- Skull: Dome with bony knobs and spikes
- Lived: Late Cretaceous
- Region: North America
It had bony knobs and spikes on its skull.
*Stegoceras* lived during the Late Cretaceous in North America.
3. Dracorex
Dracorex hogwartsia, named for its dragon-like skull and inspired by the Harry Potter series, had a flat skull with spikes and knobs rather than a fully developed dome. It is thought by some scientists to be a juvenile or subadult form of Pachycephalosaurus. It lived in North America during the Late Cretaceous.
- Skull: Flat with spikes and knobs
- Possible juvenile form of Pachycephalosaurus
- Lived: Late Cretaceous
- Region: North America
Dracorex's skull is flat with spikes and knobs, unlike the heavily domed skulls of adult pachycephalosaurids.
Dracorex may represent a juvenile or subadult stage.
Dracorex is known for its dragon-like skull, lived in the Late Cretaceous, and fossils were found in North America.
4. Micropachycephalosaurus
Despite its name, Micropachycephalosaurus had a relatively flat skull and is considered one of the more basal or primitive members of Pachycephalosauridae. It was much smaller than Pachycephalosaurus, measuring only about 1 meter in length. Fossils have been found in Asia, specifically China.
- Size: About 1 meter long
- Skull: Relatively flat
- Region: Asia (China)
- Lived: Late Cretaceous
It was smaller and had a more primitive, less developed skull dome.
Fossils were discovered in Asia, specifically China.
*Micropachycephalosaurus* was small, had a flat or lightly domed skull, and its fossils were found in Asia.
Pachycephalosauridae includes some of the most visually distinctive dinosaurs known, with their thick, often elaborately ornamented skulls. Key genera like Pachycephalosaurus, Stegoceras, and Dracorex showcase the diversity within this family, which thrived during the Late Cretaceous in North America and Asia.
- Pachycephalosaurids are known for thick, domed skulls used for combat or display.
- Prominent examples include Pachycephalosaurus, Stegoceras, Dracorex, and Micropachycephalosaurus.
- Lived mainly in North America and Asia during the Late Cretaceous.