There's a new dinosaur in town, and it's pretty damn strange. Despite being related to famous meat-eaters like the Velociraptor and the T. rex, the 3-meter-long Chilesaurus diegosuarezi was a plant eater. Armed with a horned beak, two-finger hands, and a proportionately small head and feet reminiscent of long-necked dinosaurs, Chilesaurus is the ultimate weirdo. Indeed, paleontologists think it's so odd-looking that they've taken to comparing it to the platypus — a duck-billed, beaver-tailed, egg-laying mammal. And now that they've found this curious creature, scientists are on the lookout for more.
"I honestly think that no paleontologists expected early theropods could have ever evolved into something like this," says Alexander Vargas, a paleontologist at the University of Chile and a co-author of the study published in Nature today. The discovery is "more than merely a new species — this is a fundamentally new body-plan within dinosaurs."
Chilesaurus Credit: Gabriel Lío / Platypus credit: Klaus / Flickr
"Chilesaurus is an evolutionary hodgepodge."
Chilesaurus was discovered by Diego Suarez, a seven-year-old boy in Chile, in 2004. He found the fossils in rocks that were deposited at the end of the Jurassic Period — about 145 million years ago — at the Toqui formation, south of the Chilean Patagonia. Because of the dinosaurs' strange combination of features, researchers originally assumed that the fossils belonged to more than one species. A more extensive analysis revealed otherwise, however.
"I think it may deserve to be called ‘the platypus of dinosaurs,' because, like the platypus, it is very old lineage with many primitive features, that nevertheless underwent great evolutionary transformations, combining traits of radically different animals," Vargas says.
Chilesaurus stands out from the rest of the crowd because of its beak, uncurved claws, and leaf-shaped teeth. Its hips resemble that of the herbivorous dinosaurs, while its hindfeet — feet that are wide and four-toed, as opposed to slender and three-toed, like most of its carnivorous relatives — resemble those of more primitive dinosaurs. Even though Chilesaurus is related to the dominant group of carnivores at the time, it was on a strictly meat-free diet. This isn't entirely new; T. rex has other herbivorous relatives. But those species came later, and they were more closely related to birds than Chilesaurus. This means that a plant-based diet was acquired by theropods — the group of dinosaurs to which both T. rex and Chilesaurus belong — far earlier than originally thought. "Chilesaurus is an evolutionary hodgepodge with a remarkable mixture of primitive and advanced traits," says Lawrence Witmer, a paleontologist at Ohio University who didn't participate in the study.
"The platypus of dinosaurs."
The fact that Chilesaurus was so unlike other dinosaurs at the time is unexpected, Witmer says. Dinosaurs that lived in Chile, Tanzania, and Wyoming all looked pretty similar at the time, "so to find a legitimate oddball tucked away in Chile" is unusual. It'll be exciting to see whether it is "an isolated evolutionary one-off" or a member of a larger, equally weird group of dinosaurs "that may have had a more global reach," he says.
Credit: Gabriel Lío
Overall, the work done by Vargas and his team is solid, Witmer says. But other researchers may object to the fact that most of the bones of the skull are still missing. "We are pretty convinced that Chilesaurus is an early theropod, but other scientists may dispute that conclusion," Vargas says. One way to convince them will be to recover more skull materials. That's on their to-do list, he says.
The researchers are also on the lookout for other, weird-looking relatives of Chilesaurus. If scientists can find fossils belonging to intermediate species — species that make the evolutionary link between between early carnivorous theropods and the highly transformed Chilesaurus — it might help them understand how Chilesaurus got to be so strange. Finding other relatives would also support the idea that the dinosaur wasn't just an evolutionary blip. "Chilesaurus is a truly mind-bending lesson in terms of the actual evolutionary possibilities of dinosaurs," Vargas says. "It's a cautionary benchmark: radically new forms of dinosaurs may still be discovered."
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