First Canadian 'dinosaur' closely related to mammals

The first 'dinosaur' fossil named from Canada has been shown to have steak knife-like teeth, indicating that the species is more closely related to mammals than to dinosaurs, scientists say.
The researchers from University of Toronto Mississauga (UTM), Carleton University and the Royal Ontario Museum have changed its name to Dimetrodon borealis - marking the first occurrence of a Dimetrodon fossil in Canada.
"It's really exciting to discover that the detailed anatomy of the teeth has finally allowed us to identify precisely this important Canadian fossil," said lead author Kirstin Brink, who did the research while at UTM.
"Dimetrodon is actually more closely related to mammals than it is to dinosaurs," said Brink.

In fact, it is believed they went extinct some 40 million years before the dinosaurs.
The fossil, previously known at Bathygnathus borealis, was collected in 1845 while a farmer was digging out a well on his property at the Prince Edward Island in Canada.

It was sold to the Academy of Natural Sciences in Philadelphia, where a paleontologist Joseph Leidy studied and named it.
Leidy named the fossil Bathygnathus (meaning deep jaw) borealis (from the north) because he mistook it as the lower jaw of a dinosaur, similar to the large bipedal species that were being collected in Europe at the time.

The Bathygnathus specimen was the first 'dinosaur', and the second vertebrate fossil named from Canada (Dendrerpeton, an extinct amphibian from Nova Scotia, was named by Sir Richard Owen two months earlier).
Several paleontologists have studied the Bathygnathus specimen since it was first named, but its precise identity was unknown.
For example, it was unclear whether it had Dimetrodon's signature dorsal sail - created by tissue stretched between spines sticking up from its backbone - or lacked a sail like its smaller cousin Sphenacodon.
Using family trees and imaging techniques to see the internal anatomy of the fossil, researchers found that the eight preserved teeth linked the fossil to the Dimetrodon family - the first terrestrial animal to have "ziphodont" teeth.

"These are blade-like teeth with tiny serrations along the front and back of the teeth, similar to a steak knife," said senior author Robert Reisz, of UTM.
"The roots of these teeth are very long, around double the length of the crowns. This type of tooth is very effective for biting and ripping flesh from prey," Reisz said.
Fossils of Dimetrodon have now been found in the US, Canada and Germany.
The study was published in the Canadian Journal of Earth Sciences.