A Troodon, one of the small carnivores characteristic of Alberta dinosaurs, tries to catch a toothed bird. (Artwork: Jan Sovak)
(Edmonton) A University of Alberta researcher who spent six years combing through collections of fossilized dinosaur teeth has now identified more than 20 species of small meat-eating dinosaurs.
As a U of A undergraduate and master’s student, Derek Larson examined thousands of dinosaur teeth found in western North America. Larson’s research supervisor, U of A paleontologist Philip Currie, says the findings are quite an accomplishment, enabled by the university’s encouragement for undergraduate students to get involved in research projects.
“Derek was able to expand our identification of small, two-legged meat-eaters that roamed Western Canada and the U.S. from seven species to at least 23,” said Currie.
The researchers say these two-legged dinosaurs ranged from the size of a chicken to two metres long. In most cases, tooth fossils are all that remains of small dinosaurs.
“It’s the same situation you have in today’s world with the remains of small animals like weasels,” said Currie. “Because the bones are light and small in size, after the animal dies the bones scatter, and if they’re not covered by sand or mud they disintegrate very quickly.”
Luckily, the researchers do have fossilized skeletons with teeth for some of the small meat-eaters. For example, Troodon is a two-legged meat-eater about two metres in length, and Alberta is one area where its fossils have been found.
“We were able to link some previously unidentified fossilized teeth as being from relatives of Troodon,” said Currie. They were obviously similar teeth, but were not the same. Comparison with other species represented by teeth and bones gave the researchers a way to establish that other tooth samples also must have belonged to small dinosaur species that no one had previously identified.
The researchers say the huge increase in the number of identified small meat-eating species shows that instead of a few species existing for many millions of years, there were actually many small meat-eating species, each existing for shorter time periods.
“Given that today there are more small animals than large, it’s really not surprising that during the age of the dinosaurs there were lots of small dinosaur species as well,” said Currie.
The research by Currie and Larson (now at the University of Toronto) was published Jan. 23 in the journal PLOS ONE.