智利发现奇异“鸭嘴兽式”恐龙

Although closely related to the notorious carnivore Tyrannosaurus rex, a new lineage of dinosaur¹ discovered in Chile is proving to be an evolutionary² jigsaw³ puzzle, as it preferred to graze upon plants. Palaeontologists are referring to Chilesaurus diegosuarezi as a 'platypus⁴' dinosaur because of its bizarre combination of characters that resemble different dinosaur groups. For example, Chilesaurus boasted a proportionally small skull⁵, hands with two fingers like Tyrannosaurus rex and feet more akin⁶ to primitive⁷ long-neck dinosaurs⁸.

 

Chilesaurus diegosuarezi is nested within the theropod group of dinosaurs, the dinosaurian⁹ group that gathers the famous meat eaters Velociraptor, Carnotaurus and Tyrannosaurus, and from which birds today evolved. The presence of herbivorous theropods was up until now only known in close relatives of birds, but Chilesaurus shows that a meat-free diet was acquired much earlier than thought.

 

Chilesaurus diegosuarezi is named after the country where it was collected, as well as honouring Diego Suárez, the seven year old boy who discovered the bones. He discovered the fossil remains¹⁰ of this creature at the Toqui Formation in Aysén, south of Chilean Patagonia, in rocks deposited at the end of the Jurassic Period, approximately 145 million years ago.

 

Diego was in the region with his parents, Chilean geologists¹¹ Manuel Suarez and Rita de la Cruz, who were studying rocks in the Chilean Patagonia, with the aim to better understand the formation of the Andes mountain range. Diego stumbled across the fossils while him and his sister, Macarena, were looking for decorative¹² stones.

 

Due to Chilesaurus' unusual combination of characters, it was initially¹³ thought that Diego had uncovered several species. However, since Diego's find, more than a dozen Chilesaurus specimens¹⁴ have been excavated¹⁵, including four complete skeletons -- a first for the Jurassic Period in Chile -- and they demonstrate that this dinosaur certainly combined a variety of unique anatomical traits.

 

Most of the specimens are the size of a turkey, but some isolated¹⁶ bones reveal that the maximum size of Chilesaurus was around three metres long. Chilean and Argentinian palaeontologists from institutions including the University of Birmingham, along with Diego's parents, have been studying these skeletons, with the findings published in full in Nature on April 27th.

 

Other features present in very different groups of dinosaurs Chilesaurus adopted were robust¹⁷ forelimbs similar to Jurassic theropods such as Allosaurus, although its hands were provided with two blunt fingers, unlike the sharp claws of fellow theropod Velociraptor. Chilesaurus' pelvic girdle resembles that of the ornithischian dinosaurs, whereas it is actually classified in the other basic dinosaur division -- Saurischia.

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