A newly identified primitive mammal-like animal was agile, sleek and had a voracious appetite for meat.
The animal, identified as a varanopid pelycosaur and part of the genus Aerosaurus, looked like today's Komodo dragons, but was actually more closely related to mammals, according to a study published in the journal Naturwissenschaften (The Science of Nature).
"Our varanopid was probably about the size of an adult Nile monitor found in Africa," co-author Sean Modesto told Discovery News.
"It would have looked superficially like one too. The curvature of the teeth (the tips curve back towards the throat) and the serrations on the cutting edges of these teeth suggest that the animal was equipped to rip flesh from vertebrate prey."
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One of the world's most successful fossil hunters, Roger Smith, found and collected the specimen, which consists of a partial skull and jaw. Smith, another co-author, discovered the remains in rocks from the Pristerognathus Assemblage Zone of the Beaufort Group, South Africa.
The carnivore is the youngest known primitive mammal-like mammal. It lived about 260 million years ago during the Permian Period and was part of "the first wave of creatures on the evolutionary line to mammals," said Modesto, an associate professor of biology at Cape Breton University.
Modesto and his team studied the fossils. The remains, along with prior finds, indicate the mammal-like predators survived for more than 35 million years and, toward the end of their time on Earth, co-existed with more advanced animals.
"Advanced" in this case refers to mammal-like characteristics that evolved to varying degrees in species of the period.
Christian Sidor, curator of vertebrate paleontology and an associate professor of biology at the University of Washington, agrees that the fossils belonged to a varanopid.
Sidor told Discovery News that the newly discovered protomammal "represents an upward extension for varanopids." He wishes more fossils for the predator existed.
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As it stands, Modesto and his team can still tell that the new Aerosaurus had a more primitive body design. It's a design that proved to be successful.
"These animals were the most agile predators of their time, sleek-looking when compared to their contemporaries," co-author Robert Reisz from the University of Toronto Mississauga 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."
Aerosaurus's razor sharp teeth, with their finely serrated cutting edges, are typical of hypercarnivores. These are animals with a diet consisting of more than 70 percent meat. It's doubtful then that the new mammal-like predator sunk its specialized choppers into plants very often.
The body plan survives to this day to some extent in Komodo lizards. Aerosaurus wasn't even related to these monitor lizards, according to the researchers.
"The resemblances are superficial because of convergent evolution: animals that have adapted to similar life styles often converge on the same body plans," explained Modesto.
Aerosaurus eventually died out. Another protomammal group, called the cynodonts, gave rise to mammals. The cynodonts appeared some 1-3 million years after the lifetime of the newly identified varanopid. It then took another 35 million years of evolution before the first actual mammals emerged.