Pachycephalosaurus wyomingensis

Image courtesy

Pachycephalosaurus wyomingensis, the “Thick-headed dinosaur” is one of the most curious of all dinosaurs.  Named for its most unique feature, greatly thickened frontal and parietal bones of its skull, Pachycephalosaurus (“Pachy” = thick, “cephalo” = head, “saurus” = lizard) has a dome-shaped skull that may be as much as 10 inches (25 cm) thick.  Although the domed skull gives the animal the appearance of super intelligence, it has, in fact, a very small brain that sits underneath the huge domed skull. In the picture below, you can see the dome of an adult Pachy skull, ornamented with an array of subtending horn-like appendages.

Pachycephalosaurus was a medium-sized dinosaur ranging up to about 15 feet (5 meters) in length. It weighed hundreds of pounds upward to perhaps a ton or more. The teeth are small, with jagged leaf-shaped crowns (see closeup on right) that appear to be designed for a diet of plants.

Several notable skulls of Pachycephalosaurus wyomingensis have been found on the Hanson Ranch. Among them are one of the largest Pachy skulls ever found and one of the smallest!  The small skull is a cast.  The larger one is part of the Museum collection, and a 3DVR (Three Dimensional Virtual Reality) movie of the skull can be seen here.

As you can well imagine, the behavior of these remarkable creatures has been the subject of a wide variety of speculation since their discovery in Niobrara County, Wyoming in 1930 by George Sternberg.  The type specimen (the specimen that serves to define and name a new species) collected by Sternberg was described and named by G.K. Gilmore in 1931. It may have come from the very Ranch where we are now working in Niobrara County, Wyoming!

In any case, as the specimen became better known, the unique thickened skull begged for an explanation. While nobody knows what the true function of the thickenings of the skull was, the most popular explanation is that it was used in some kind of head-butting routine during courtship rituals or perhaps as a defensive organ to ward off potential predators. Have another suggestion? It could possibly be the correct one.  What do you think?

The diorama depicts two Pachycephalosaurids in a head-butting contest.

Below is a Pachyocephalosaurus skeleton in jigsaw puzzle form.  If you can correctly assemble the puzzle you will be admitted to the portion of the collection with all of thePachycephalosaurus bones. (To skip the puzzle, click on the link below the puzzle.)

Skip the puzzle! Take me to the Museum!
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