Today, Caleb Brown and colleagues announced the discovery of Canada’s newest dinosaur, Thescelosaurus assiniboiensis – the first new dinosaur species to be discovered in Saskatchewan since 1926. The new dinosaur is named after the historic District of Assiniboia, where it was found. The small-bodied, two-legged plant-eater lived alongside the famed Tyrannosaurus rex and Triceratops, at the very end of the age of dinosaurs.
The 66 million year old skeleton assigned to the new species was collected from the Frenchman River Valley in southwestern Saskatchewan in 1968 by Albert E. Swanston while working for the Saskatchewan Museum of Natural History (now the Royal Saskatchewan Museum). After almost 40 years, it was studied as part of a Masters thesis by Caleb Brown, then at the University of Calgary, and named by him this week in the Zoological Journal of the Linnean Society. Caleb now resides at the ROM, where he continues his work on the evolution of plant-eating dinosaurs under my supervision at the University of Toronto.
Thescelosaurus assiniboiensis would have had a long head with a bird-like beak, and teeth in both the front and back of the mouth. It lacked obvious defensive structures such as armor or horns. Although similar dinosaur species have been found in Montana, Wyoming and the Dakotas, Thescelosaurus assiniboiensis has a number of unique traits that distinguish it from its close relatives. These include the shape of the back of skull and its hip structure, which is more similar the ROM’s Parksosaurus from Alberta than it is to other species of Thescelosaurus.
Thescelosaurus assiniboiensis, being about the size of the white-tailed deer, is one of the smallest known plant-eating dinosaurs at the end – Cretaceous – a tumultuous period in Earth’s history that ended in the extinction of the dinosaurs. Its discovery illustrates that small-bodied dinosaurs were more diverse, and potentially more abundant, facing the end Cretaceous extinction even than had previously been thought. This is particularly interesting when the large-bodied dinosaurs, which are better known, appear to show a decrease in diversity (see some new ROM research into the K-T extinction here: http://evanslab.wordpress.com/2011/09/28/goodbye-anatotitan/ ).
This new species is Caleb’s first dinosaur, but more are on the way. We have several projects describing new dome-headed and horned dinosaurs that will appear in the near future – so stay tuned.
Brown, C. M. Boyd, C. A., Russell, A. P. 2011. A new basal ornithopod dinosaur (Frenchman Formation, Saskatchewan, Canada), and implications for late Maastrichtian ornithischian diversity in North America. Zoological Journal of the Linnean Society. 163: 1157-1198.