A newly discovered dinosaur fossil displays such a bewildering collection of characteristics and features that paleontologists have taken to calling it the "platypus" dinosaur.
Although closely related to meat-eating dinosaurs of the typically two-legged theropod group such as Tyrannosaurus rex, Velocipraptor and Carnotaurus, the new fossil, discovered in Chile, shows this dinosaur was a strict vegetarian, researchers say.
The new find has been named Chilesaurus diegosuarezi, after the country where it was discovered and for the 7-year-old boy, Diego Suárez, who discovered it.
Diego was south of Chilean Patagonia with his geologist parents, who were there conducting studies to better understand the formation history of the Andes mountain range, when he stumbled across the fossil bones of the unusual dinosaur.
The odd variety of anatomical features at first had paleontologists believing the young boy had uncovered a mixed group of fossil bones of several species, but subsequent discovery of more than a dozen Chilesaurus confirmed the discovery of a new dinosaur previously unknown to science.
Fossils have shown Chilesaurus had a rather small skull, forelimbs with two fingers like the carnivorous T. rex, but feet more like those of primitive long-necked herbivore dinosaurs, researchers say. It grew up to about 10 feet long.
Despite having meat-eating cousins, Chilesaurus preferred a vegetarian diet, they say, and could feed on plants either using its long neck to reach them or using its T. rex-like forearms to grab vegetation and stuff it into its bird-like beak.
"Chilesaurus probably fed upon ferns, araucarians, bennetitaleans, and podocarps -- all of which were plants that were abundant at the end of the Jurassic," says Fernando Novas of the Bernardino Rivadavia Natural Sciences Museum in Buenos Aires, lead author on a study of the fossil published in Nature.
While some of the theropod species would eventually evolve into birds, Chilesaurus - and similar vegetarian relatives living around 145 million years ago - hit an evolutionary dead end, Novas suggests.
"Theropods that evolved into herbivores finally went extinct without leaving descendants that switched into carnivores again," he says.
Paul Barrett of The Natural History Museum in London calls Chilesaurus a truly bizarre animal and ranks it one of the most unusual dinosaur discoveries of the past three decades.
"It has an exceptionally odd mixture of features, so much so that if you found these bones separately, rather than together, you would probably end up placing each bone in different dinosaur groups," he says.