Giant Croc-Like Beasts Hunted Africa’s Dinosaurs 210 Million Years Ago

Artist's reconstruction of two rauisuchians fighting over a dead mammal relative during the Triassic in southern Africa. Viktor Radermacher, owns copyright

Triassic vegetarian dinosaurs lived in fear of huge, croc-like beasts that grew up to 10 meters (33 feet) long and were equipped with serrated, curved gnashers. Known as the rauisuchians, they roamed most of the world and went extinct 200 million years ago. A new study of fossils from southern Africa reveals insights into some of the last survivors of this fearsome group and shows they lived surprisingly close to the Antarctic circle, pushing their bodies to their absolute limits.

Reporting their findings in the Journal of African Earth Sciences, a team from the University of Witwatersrand re-analyzed bones left behind by rauisuchians in the Elliot Formation in Lesotho and South Africa. Their specimens included teeth, parts of jaws, body armor, and hind leg bones. Between them, these fossils represented two different kinds of rauisuchian.  

“These ancient fossils provide us with evidence of how at least two predator species hunted vegetarian dinosaurs 210 million years ago,” said first author and master’s student Rick Tolchard in a statement. “It is amazing to follow the clues left behind in fossilized teeth, jaws, limbs and other fossils to help us tell the ancient story of life in southern Africa.”

Rick Tolchard with the fossil of a rauisuchian from Namibia. Helke Mocke 

While these ancient relatives of crocodilians came in a variety of shapes and sizes, the southern African fossils are some of the largest members of the group. Maxing out at about 10 meters (33 feet), these giants had huge skulls ready to chomp down on herbivorous dinosaurs and therapsids (reptilians related to mammal ancestors) that looked tasty. The researchers note that the predators would have had an abundance of creatures to feed on in southern Africa at the time.

"Rick's study demonstrates the value of re-examining old specimens, and now we finally know what was preying on all those herbivorous dinosaurs!" said Tolchard’s advisor Professor Jonah Choiniere.

Rauisuchian teeth housed by the University of Witwatersrand. Wits University  

The rauisuchians were an order of archosaurs, a large group of reptilian creatures that includes the dinosaurs, extinct crocs, pterosaurs, as well as the birds and crocodilians alive today. Back in the Middle to Upper Triassic, they were top predators and were especially large for non-dinosaurs. In fact, their remains have been mistaken for dinosaurs and their relatives before. When they died out around 200 million years ago, they left a hole to be filled by large, carnivorous dinosaurs.

The team note in their paper that rauisuchian fossils have been found in multiple layers of rock in the Elliot Formation, suggesting  there could be more bones waiting to be uncovered. They hope that future finds will help us learn more about this strange and somewhat mysterious group of toothy Triassic beasties.

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