Named By: David C. Evans, Ryan K. Schott, Derek W. Larson, Caleb M. Brown, Michael J. Ryan - 2013.
Classification: Chordata, Reptilia, Dinosauria, Ornithischia, Pachycephalosauridae.
Species: E. audeti (type).
Size: Estimated to be about 1.8 meters long and 40Kg in weight.
Known locations: Canada, Alberta - Milk River Formation, Deadhorse Coulee Member.
Time period: Santonian of the Cretaceous.
Fossil representation: Skull fragments including two domes.
so far only represented by skull fragments, Acrotholus
was still a
very exciting discovery. At the time of its description, Acrotholus
was the oldest confirmed pachycephalosaur
dinosaur from the North
American continent. Also important is that like most other known
pachycephalosaurs, Acrotholus already had a fully
dome. However the purpose of this dome is still a controversial
matter since the old ‘head bashing’ theory is not universally
accepted by all palaeontologists. It may be that the dome was a
purely visual display device for inter species recognition. The bone
in the dome of Acrotholus seems to have been over
ten centimetres thick.
The team that described Acrotholus also took the opportunity to point out that the fossil record of long extinct animals can be biased towards the preservation of larger species. Larger animals have proportionately larger bones which mean that it is harder for scavengers to consume them, often because of simple things like not having big enough mouths to fit them in. Smaller animals of course have smaller bones which mean that a greater number of meat eating creatures are able to process the bones for additional sustenance, meaning that fewer bones survive to fossilise. Indeed, if you look at the preservation of smaller animals, the best preserved individuals are usually the result of dying in more specialised circumstances such as being buried in landslides or buried in sediment at the bottom of a water system. Another 2013 naming, Albertadromeus, was used to further support this theory.
Acrotholus is not as old as some of the known pachcephalosaur genera from Asia, but it does help to complete a picture of the fauna roaming around North America earlier in the late Cretaceous. Also, now that palaeontologists have a better idea of what is out there, Acrotholus may be the first of many more Santonian age pachycephalosaurs.
The genus name Acrotholus means ‘high dome' which is a reference to the dome shaped skull that the genus had. The species name ‘audeti' is in honour of Roy Audet, a rancher on whose land the holotype specimen was discovered on in 2008.
Acrotholus may have been hunted by small predatory dinosaur genera such as Saurornitholestes and Richardoestesia, fossils for which have also been recovered from the Milk River Formation.
- ‘The oldest North American pachycephalosaurid and the hidden diversity of small-bodied ornithischian dinosaurs’, David C. Evans, Ryan K. Schott, Derek W. Larson, Caleb M. Brown, Michael J. Ryan - 2013.