Saturday, May 18, 2013

Acrotholus: Prehistoric Animal of the Week

This week I will be reviewing a newly discovered dinosaur that was just published about this month!  Acrotholus audeti was a small, (about six feet long) plant eating dinosaur that lived in what is now Alberta, Canada 85 million years ago during the Late Cretaceous.  Its genus name translates to "high dome" because of the shape of its skull.  It belonged to the dinosaur family called pachycephalosauridae and was an earlier relative of the larger and more well known Pachycephalosaurus.  These dinosaurs are characterized by having large heads with thick skulls that may have been used for display and/or as a ramming weapon.

Life reconstruction of Acrotholus audeti by Christopher DiPiazza

Acrotholus is only known from skull chunks from a few individuals, specifically the domed tops of their heads which are two inches thick.  Small dinosaurs tend not to fossilize as often as large ones because their bones are more fragile.  Since the skulls of these Acrotholus were so thick, however, they managed to preserve to be discovered by paleontologists millions of years later after they died.

One of the skull fragments from Acrotholus that was discovered.  This would have been the top of the animal's head.  Check out how thick it is! 

Acrotholus is amongst the oldest known pachycephalosaurids and is THE oldest known pachycephalosaurid native to North America.   Even though it is more basal than all the other pachycephalosaurids that lived after it, it's head is still well-developed and thick for its size.  This tells us that this adaptation, which is common in varying forms throughout the family, probably evolved much earlier than the time of Acrotholus

That's all for this week!  As always feel free to comment below or on our facebook page.  If there is a dinosaur or other prehistoric creature you want to see reviewed and illustrated let me know! 


Evans, D. C.; Schott, R. K.; Larson, D. W.; Brown, C. M.; Ryan, M. J. (2013). "The oldest North American pachycephalosaurid and the hidden diversity of small-bodied ornithischian dinosaurs". Nature Communications 4: 1828. doi:10.1038/ncomms2749

"Cleveland Museum of Natural History." Acrotholus Audeti. N.p., n.d. Web.

"Oldest? New 'Bone-Head' Dinosaur Hints at Higher Diversity of Small Dinosaurs." ScienceDaily. ScienceDaily, 07 May 2013. Web.


  1. Excelent again. I'm planing on getting a safari vagaceratops. Could you do that as my next request(I hope I'm. Not the only one who makes them)

    1. This Sunday is by request something different. I can aim for next week!

  2. I heard it & other pachycephalosaurs may have had quills.

    1. Emphasis on the "may". As in probably did not. 0 fossil evidence for quill-like structures in any pachycephalosaur. In fact, we only have them in Psittacosaurus, which was a basal offshoot of the ceratopsian tree, and Tianyulong, a heterodontosaur. Assuming they were in pachycephalosaurs is a bit far-fetched, but I suppose not genetically impossible.