Scientists have identified the oldest known relative of the dinosaurs and are expressing surprise at how little it resembled one.
Researchers on Wednesday described fossils of a long-necked, four-legged, meat-eating reptile called Teleocrater rhadinus. It reached up to 10 feet long and prowled across what is now Tanzania, in East Africa, about 245 million years ago.
Teleocrater lived during the Triassic Period, millions of years before the first dinosaurs. Scientists called it a close cousin rather than a direct dinosaur ancestor.
Its appearance, part crocodile and part dinosaur, was different from what scientists had expected from the earliest members of the dinosaur family tree.
“I’m surprised by the mosaic” — or mix — “of features that it possesses,” said Kenneth Angielczyk, one of the researchers in the study, which was published in the journal Nature.
“In terms of how it shakes up our understanding of dinosaur evolution, Teleocrater shows that the earliest members of the dinosaur lineage,” or family tree, “were very unlike dinosaurs,” Angielczyk said.
Dinosaurs belong to a larger group called archosaurs (ARK-uh-sores). About 250 million years ago, that group split into two branches: crocodilians (which include alligators and crocodiles); and another branch that includes dinosaurs, birds and extinct flying reptiles called pterosaurs (TARE-uh-sores). Teleocrater is the oldest-known member of the dinosaur-pterosaur-bird branch.
Scientists had expected such a dinosaur forerunner to be a smallish, two-legged predator. Although dinosaur predators had two legs, the teleocrater instead was four-legged. It looked similar to a Komodo dragon, a large lizard that lives in Indonesia.
Virginia Tech paleontologist Sterling Nesbitt, the study’s main author, said fossils of at least four teleocraters were found in southern Tanzania.
Unlike a dinosaur, the teleocrater had ankle joints that could rotate from side to side and flex up and down, giving it a crocodile-like walking style.
Teleocrater’s remains were found in the same Tanzanian region as fossils of the two-legged meat-eater nyasasaurus, which lived perhaps 2 million years later. Some scientists regard nyasasaurus as the earliest-known dinosaur.