Plants and Animals

Discovery Of Early Dinosaur “Cousin” Does Not Look Like Scientists Thought

Paleontologists have got some things not quite right about dinosaurs throughout the years and understandably so – they’re working with dust, sap, and bones from millions of years ago. But now, a once-in-a-lifetime discovery changes the very look and history of early dinosaur relatives.

“Surprisingly, early dinosaur relatives were pretty profoundly not dinosaur-like,” said co-author Ken Angielczyk, The Field Museum’s associate curator of fossil mammals, in a statement. In a study published in Nature, the team introduces to the world to Teleocrater rhadinus.

The 6-foot (1.8-meter) carnivore had a long neck and an even longer tail, with a weight that clocked in at 20-65 pounds (9-30 kilograms). It stood 2 feet (0.6 meters) at the hip and had quite the swagger – its ankle joints could rotate from side to side as well as flex up and down. 

This might sound like a typical dinosaur, but it’s actually not the gait of dinosaurs or birds as we know it. Instead, it’s more similar to the splayed walk of modern crocodiles.

This is an incredible find as it thwarts previous assumptions about the family tree of dinosaur relatives. The discovery tells researchers that the earliest cousins of dinosaurs had many features in common with crocodilians. Its jaw muscles, however, are much more similar to bird-like archosaurs with the attachments at the back of its skull.

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Life reconstruction of the new species Teleocrater rhadinus, a close relative of dinosaurs. Credit: Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (Buenos Aires, Argentina), artwork by Gabriel Lio.

All dinosaurs belong to a group called archosaurs (“ruling reptiles”), which contain dinosaurs, birds, and crocodilians. However, 250 million years ago, that group split into two – one was bird-like with dinosaurs, birds, and pterosaurs, and the other crocodile-like with alligators, crocodiles, and some now-extinct relatives. T. rhadinus is the earliest discovery of the bird-like side of the family (check image below).

It’s important to note, Teleocrater is not a dinosaur, but instead part of a lineage separate from dinosaurs.

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“Based on previously available fossils, paleontologists thought that the earliest members of this lineage probably were fairly dinosaur-like in many ways (i.e., they were probably small, lightly built, bipedal animals with upright limbs and hinge-like ankles),” said Angielczyk to IFLScience. “Teleocrater obviously doesn’t fit that model; it almost looks more like a living varanid lizard than a dinosaur. It also retains a number of primitive features that it inherited from the common ancestor of bird-line and crocodile-line archosaurs.”

This means the many distinctive features found in bird-line archosaurs initially had crocodile-like features and evolved in a step-wise fashion over a longer period of time.

This “missing link” was initially discovered in the 1930s by British paleontologist Alan Charig. His discovery included many vertebrae and parts of the pelvis and limbs. However, the fossils were hardly considered a goldmine, with the connection to dinosaurs not even recognized at the time.

Image in text: A simple tree to illustrate where Teleocrater rhadinus belongs. Credit: Sterling J. Nesbitt et al.

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