Dinosaur ancestors had 'crankles' - crocodile ankles, scientists find

Sarah Knapton
Life model of the new species Teleocrater rhadinus, a close relative of dinosaurs - Museo Argentino de Ciencias Naturales

A missing link in the evolution of dinosaurs has been discovered at the National History Museum in London. 

The ancestors of dinosaurs had 'crankles' - crocodile ankles, scientists have concluded after finding a lost fossil which had been forgotten about for decades.

Fragments of a 245 million-year-old Teleocrater rhadinus were collected from rocks in the Manda Beds in southern Tanzania in the 1930s, but researchers at the time could not work out where the fossil fitted into the evolutionary tree. 

However when the bones were rediscovered recently and studied by experts from the University of Birmingham and the Fields Museum in Chicago, they realised the fossil was an early 'cousin' of the dinosaurs.

And crucially, it was a lot less dinosaur-like than they were expecting. 

Writing in the journal Nature, they found that while it had a long neck and tail, it also walked on all fours in style more like that of a modern monitor lizard, or crocodile.

Ken Angielczyk, the Field Museum's associate curator of fossil mammals and one of the paper's authors, said: "Teleocrater has unexpectedly crocodile-like features that are causing us to completely reassess what we thought about the earliest stages of dinosaur evolution.

"Surprisingly, early dinosaur relatives were pretty profoundly not dinosaur-like.

"Scientists generally don't love the term 'missing link,' but that's kind of what Teleocrater is: a missing link between dinosaurs and the common ancestor they share with crocodiles."

The new species Teleocrater rhadinus hunting a cynodont, a close relative of mammals.  Credit: Museo Argentino de Ciencias Naturales

Teleocrater, a 7ft to 10ft long and 2ft tall carnivore weighing between 20lb and 65lb (9kg to 29kg), walked the Earth during the Triassic period and pre-dates true dinosaurs by around 10 million years.

The scientists said it appeared after a large group of reptiles called archosaurs evolved into two branches; one, a bird-branch, evolved into dinosaurs and eventually birds, the other evolved into today's crocodiles and alligators.

Teleocrater is the earliest-found member of the bird branch, but was found to have ankles more like crocodiles than dinosaurs and birds, meaning it would have had a lower, more reptilian gait.

The samples, along with others discovered in the same area in 2015, were reassessed by the team, which included Dr Richard Butler from the University of Birmingham.

Dr Butler said: "Teleocrater fundamentally challenges our models of what the close relatives of dinosaurs would have looked like.

"Dinosaurs were amazingly successful animals. It's natural to want to know where they came from, and how they became so dominant.

Life reconstruction of the new species Teleocrater rhadinus, a close relative of dinosaurs.  Credit: Museo Argentino de Ciencias Naturales 

"Teleocrater is hugely exciting because it blows holes in many of our classic ideas of dinosaur origins."

The creature's name means "slender complete basin," in reference to its lean build and closed hip socket.

The NHM's Professor Paul Barrett, another main author of the paper, said: "My colleague Alan Charig would have been thrilled to see one of 'his' animals finally being named and occupying such an interesting position in the Tree of Life.

"Our discovery shows the value of maintaining and re-assessing historical collections: many new discoveries, like this one, can be made by looking through museum collections with fresh eyes."

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