Unusual new dinosaur find may be evolutionary "missing link"

But Chilesaurus had flattened teeth, which suggests it ate only plants; and an inverted, bird-like hip structure that sets it apart from the theropods. Some researchers posited that it belonged to another dinosaur group, the ornithischia.
By Joseph Scalise | Aug 19, 2017
Paleontologists are considering a major redraw of the dinosaur family tree following a new look at fossilized remains of an unusual herbivorous dinosaur unearthed in Chile 13 years ago. Writing in the latest edition of the journal Biology Letters, researchers suggested that this dinosaur may be a long-sought "missing link" between two major categories of dinosaurs.

"Chilesaurus genuinely helps fill an evolutionary gap between two big dinosaur groups," said co-author Paul Barrett, president of Britain's Palaeontographical Society and a researcher at the Natural History Museum.

The creature was the size of a kangaroo and looked like a velociraptor, with short front limbs, powerful hind legs, and an upright posture. These traits all suggested it was a member of the theropods, a major dinosaur group consisting entirely of carnivores.

But Chilesaurus had flattened teeth, which suggests it ate only plants; and an inverted, bird-like hip structure that sets it apart from the theropods. Some researchers posited that it belonged to another dinosaur group, the ornithischia.

All researchers agreed on one point: They had never seen a dinosaur like it. One paleontologist called it "the most bizarre dinosaur ever found."

Its initial discoverers lumped it in with the theropods. But in their recent study, Barrett and colleagues determined that Chilesaurus was actually an offshoot of the ornithischia. More significantly, they concluded that it might be a link between the ornithischians and their theropod counterparts--which means that the two might have been more closely related than researchers had thought.

Barrett and colleagues theorize that the two groups shared a common ancestor as early as 225 million years ago. Chilesaurus lived around 150 million years ago and may be related to this common ancestor, they said.

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