Pachycephalosauria — the thick-skulled dome-heads of the Cretaceous

When and where

Pachycephalosauria lived from 100 to 66 million years ago, spanning the middle and late Cretaceous. Their fossils surface in North America from Montana to Alberta, and across Asia in Mongolia and China. No remains have been confirmed from Europe, Africa, or the Southern Hemisphere. The entire clade vanished in the Cretaceous-Paleogene extinction event 66 million years ago.

How we know

The clade was formally named in 1974 by paleontologists Teresa Maryańska and Halszka Osmólska, based on distinctive thickened skull roofs. The best-known member, Pachycephalosaurus wyomingensis, was described by Charles W. Gilmore in 1931 from a domed skull collected in Montana. Lawrence Lambe named Stegoceras validum in 1902 from Alberta, and it remains one of the few species known from partial skeletons rather than isolated skull fragments. The domes often exceed 20 centimetres in thickness in large species, and many specimens preserve rows of bony nodes and spikes around the skull margin.

Source: https://en.wikipedia.org/wiki/Pachycephalosauria

What set it apart

Pachycephalosaurs stood out for their extraordinary skull architecture. The roof of the skull was a solid dome of bone, up to 25 centimetres thick in the largest species, surrounded by spikes and knobs that varied between genera. Some forms, such as Homalocephale, carried a flat roof; others, such as Pachycephalosaurus, grew a high dome. All were bipedal and herbivorous or lightly omnivorous, with small leaf-shaped teeth and five-fingered hands. Despite decades of work, no complete skeleton has ever been found. Paleontologists reconstruct the body from a handful of partial skeletons and a large collection of skull fragments recovered from Montana, Alberta, and Mongolia.

For collectors and classrooms

A Pachycephalosauria figure captures one of the strangest head designs in the dinosaur record. Accurate models show the thickened dome and the surrounding spikes that distinguish these animals from every other clade. The figure works well in a unit on Cretaceous herbivores or as a case study in how bone structures adapt to behaviour.

Pick up a detailed Pachycephalosauria figure here.