Life reconstruction of the new pachycephalosaurid dinosaur Acrotholus audeti in its environment
Photo Credit: artwork: Julius Csotonyi

Important new dinosaur discovery in Canada

It is possibly the oldest bone headed dinosaur in North America and possibly the world.

Illustration shows Acrotholus comparative size, about thigh-high on modern man, also showing the placement of fossil skull on the dinosaur © Caleb Brown ROM

Scientists say the newly named Acrotholus audeti, was about 2 metres long, about 40kg, and would have been about thigh high on modern man.

It would have lived about 85 million years ago, and its discovery adds new information to a generally lesser known  period, and about smaller dinosaurs. In fact there were probably many more smaller dinosaurs, than the big ones most of us are familiar with.

Dr David Evans was closely involved in the discovery. He is Curator, Vertebrate Palaeontology with the Royal Ontario Museum, and  Assistant Professor in the Department of Ecology and Evolutionary Biology at the University of Toronto. 

Dr David C Evans at the Royal Ontario Museum © ROM

A plant eater, the name Acrotholus mean “high dome” referring to its dome-shaped skull which is about 10 cm thick.  Audeti refers to Alberta rancher  Roy Audet on whose land the  best specimen was found in 2008.

The new dinosaur discovery is based on two skull ‘caps’ from the Milk River Formation of southern Alberta, where Dr Evans and his graduate students targeted their fossils search, specifically due to the age of the rock formations of this time period of about 85 million years ago.

The newer and much better specimen found in 2008, and the earlier skull fragment which had been in the ROM archives for decades © ROM


One of the skull caps had been collected by the Royal Ontario Museum (ROM) over 50 years ago. However, a  better specimen was found in 2008 by University of Toronto graduate student Caleb Brown during a field expedition organized by Dr. David Evans and Dr. Michael Ryan of the Cleveland Museum of Natural History.

 In modern ecosystems small mammals and reptiles can be very diverse and abundant.  However, fossil records for small dinosaurs are considerably  less common than large ones.  Dr Evans notes that at this point it’s not well understood whether the lack of fossils from small dinosaurs is a true reflection of dinosaur communities, or is related to the fact that fewer bones are found because they may have been more easily broken up or consumed by predators and-or whether being smaller and thinner, they are simply more prone to decay.

The discovery site of Acrotholus audeti in the Milk River Formation of southern Alberta. The small pile of rocks near the backpack marks the exact spot where the most complete specimen was found. © David Evans-ROM

 The find is the latest in a series of discoveries being made by Dr. Evans and Dr. Ryan as part of their  Southern Alberta Dinosaur Project, which aims to fill in gaps in of the record of Late Cretaceous dinosaurs and their evolution. The Milk River site in Alberta has some of the oldest fossil bearing formations in the province, but has been less studied than other very well known regions such as the so-called badlands of Dinosaur Provincial Park, and in the area around Drumheller

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