An unusual species of ancient reptile dubbed the “Frankenstein dinosaur” because it seemed to be made up of parts from unrelated species could be the missing link between plant-eaters and meat-eaters, according to research published Wednesday in the journal Biology Letters.
Known as Chilesaurus, the creature closely resembled a raptor but was actually an herbivore, Cambridge University Ph. D. student Matthew Baron and his colleagues reported in their new study. They believe it was one of the first ornithischians, a group of dinosaurs that had pelvic bones similar to birds and which included the Triceratops and the Stegosaurus.
Baron’s team analyzed data from more than 450 anatomical characteristics of early dinosaurs to place the Chilesaurus on the ancient reptiles’ family tree – and as they explained in a statement, it not only effectively fills a large gap between two of the major dinosaur groups, but also seems to explain how the divide between those two groups may have happened in the first place.
“Chilesaurus is one of the most puzzling and intriguing dinosaurs ever discovered,” explained study co-author Professor Paul Barrett from the London’s Natural History Museum. “Its weird mix of features places it in a key position in dinosaur evolution and helps to show how some of the really big splits between the major groups might have come about.”
Carnivorous dinosaurs, plant-eaters may have had common ancestor
Originally discovered in southern Chile and first described in 2015, Chilesaurus initially puzzled scientists because it possessed an unusual array of physical characteristics which made it difficult to place on the dinosaur family tree. For instance, the researchers said, its head resembles that of a carnivore, yet it had flat teeth that it would have used to grind up plant matter.
Likewise, as BBC News explained, ornithischians had long been viewed as a group of oddballs that were completely unrelated to other reptile of the era. However, the new study found that the Chilesaurus – which had legs like a Brontosaurus, hips resembling a Stegosaurus and a body and arms like those of a Tyrannosaurus rex – was a member of this group, suggesting that carnivores and ornithischians were more closely related than experts had previously believed.
“We had absolutely no idea how the ornithischian body plan started to develop because they look so different to all the other dinosaurs. They have so many unusual features,” Baron told the UK news outlet on Tuesday. “In the 130 years since the ornithischian group was first recognized, we have never had any concept of how the first ones could have looked until now.”
“Now that we think ornithischians and meat-eating dinosaurs such as Tyrannosaurus are related. Chilesaurus slots exactly in between the two groups. It is a perfect half-and-half mix,” he added. “So, suddenly in the new tree it makes a whole lot of sense.” Likewise, his co-author Barrett said that Chilesaurus should provide new insight into how the dinosaur groups split from one another and ultimately wound up evolving along different paths.
The findings suggest that the dinosaur family tree needs to be rewritten, and that both the bird-hipped and the lizard-hipped dinosaurs evolved from a common ancestor – a claim which runs contrary to more than 100 years of dinosaur evolutionary theory, according to the authors. They hypothesize that the two branches likely emerged due to dietary changes for Chilesaurus, as the creature changed from a meat-eater to a plant-eater, “possibly even out of necessity.”