The species of ancient, agile predators called varanopids with saw-like teeth and sleek bodies survived for more than 35 million years and co-existed with more advanced animals, they said.
Sean Modesto of Cape Breton University and Robert Reisz of the University of Toronto Mississauga performed a detailed examination of the partial skull and jaw of a varanopid "pelycosaur," a primitive, mammal-like animal that they believe lived over 260 million years ago.
"These animals were the most agile predators of their time, sleek-looking when compared to their contemporaries," Reisz said. "They seem to have survived a major change in the terrestrial fauna that occurred during the Middle Permian, a poorly understood extinction event in the history of life on land."
The configuration of the fossil teeth are typical of hypercarnivores, animals with a diet that consists of more than 70 percent meat, the researchers said.
"These ancient animals really looked like modern goannas or monitor lizards, but are actually more closely related to mammals," Modesto said.
The findings have been published in the journal Naturwissenschaften -- The Science of Nature.