Pachycephalosaurus wyomingensis – Late Cretaceous Bone-head

A young dinosaur fan sent us an email the other day, wanting to know why the dinosaur group known as the Pachycephalosauridae (the taxonomic name for the dinosaurs known as the bone-headed dinosaurs) were named after Pachycephalosaurus when more is known about another North American bone-headed dinosaur Stegoceras.

It is true that Stegoceras is one of the best known genera of the Pachycephalosaurid family.   Dozens of skull fragments are known as when as elements of the skeleton.   Indeed, most of the reconstructions of these Late Cretaceous dinosaurs are based on the scientific information available on Stegoceras.

These particular dinosaurs were among the last of the dinosaurs to evolve.  It seems that these animals were small, bipedal dinosaurs with slight skull thickenings and as the Cretaceous progressed they evolved spectacular skull ornamentation and became much larger.

Pachycephalosaurus is the largest genus of this type of bone-headed dinosaur known.  It was formerly named and described in 1943, based on skull material and studies carried out on fossils found in the northwestern part of the United States during the late 1920s and early 1930s by Charles Gilmore.  It was Gilmore who studied the first almost complete skull of this dinosaur, the fossil having been discovered in the Lance Formation of Late Cretaceous strata (Wyoming).  The name means “thick headed lizard”, very appropriate as the dome on the top of its head was over 20 cm thick (attested to by the holotype material).  As Pachycephalosaurus seemed to have the biggest bone-head of them all, this name was taken to represent this particular family of Ornithischian dinosaurs.  The first references to Pachycephalosaurines were used in scientific papers just a couple of years after the genus Pachycephalosaurus was formerly named.   Following a review and revision of this particular clade in 1974 the name Pachycephalosauridae was accepted as the term to describe all members of the bone-headed dinosaurs.

An Illustration of the Giant Pachycephalosaurid – Pachycephalosaurus

Picture Credit: Everything Dinosaur

To view a model of Pachycephalosaurus and other dinosaur models: Dinosaur Toys and Dinosaur Models

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