‘Missing link’ bolsters bold theory on dinosaur evolution

PARIS — An oddball, vegetarian dinosaur with the silhouette of a flesh-ripping velociraptor, whose fossilized remains were unearthed in southern Chile 13 years ago, is a missing link in evolution, researchers said on Wednesday.

A revised assessment of the kangaroo-sized Chilesaurus, reported in the journal Biology Letters, bolsters a theory unveiled earlier this year that threatens to upend a longstanding classification of all dinosaurs.

Dinosaurs were the monarchs of Earth for 160 million years until a space rock collided with the planet 65.5 million years ago and wiped out those confined to land.

The survivors, which could fly, are the direct ancestor of today’s birds.

“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.

When first presented to the world in 2015, Chilesaurus — despite its penchant for plants — was lumped together with theropods, the suborder of meat-eating dinos that not only includes fleet-footed velociraptors but Tyrannosaurus rex, the ultimate carnivore.

Experts acknowledged at the time, however, that it was an awkward fit. One described the beast as “the most bizarre dinosaur ever found”.

An upright posture, powerful hind legs and foreshortened front limbs were all reminiscent of theropods. But an inverted, birdlike hip structure and flattened, leaf-shaped teeth — proof of an exclusively vegetal diet — suggested that it also shared traits with another major suborder, the ornithischia.

Well-known ornithischians include Triceratops and the 3-ton Stegosaurus.

“Our reorganization was putting Ornithischia and theropods much closer together, and this new animal helps cement that relationship,” Barrett said.

The new findings support the idea that theropods and ornithischians shared a common ancestor as early as 225 million years ago.