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时间:2019-03-07 12:11:00166网络整理admin

By Rob Edwards in Edinburgh WHAT may be the world’s oldest stegosaurus has been identified from fossil bones discovered two years ago on the Scottish island of Skye. This has given palaeontologists a unique insight into the dinosaurs that could have roamed North America 175 million years ago during the Middle Jurassic. At the time, North America was still attached to Europe in the supercontinent Pangea. As mountain ranges separated Scotland and North America from the rest of Pangea, any dinosaurs found in Scotland probably also lived in North America, where direct evidence for Middle Jurassic dinosaurs is very sparse. The fossils were found in 1997 in a chunk of sandstone on the Isle of Skye by Colin Aitkin, a tourist who was exploring the shoreline. Neil Clark, a palaeontologist at the Hunterian Museum of the University of Glasgow, says the fossils are parts of the ulna and radius from the lower forearm of a 4-metre-long stegosaur or possibly an ankylosaur. Both these armour-plated herbivores survived for 110 million years until dinosaurs died out at the end of the Cretaceous. Clark believe it is more likely to be a stegosaur because of the shape of the ulna, though he cannot be certain. He is announcing the find this week as part of Scottish Geology Week, an event organised by the government conservation agency Scottish Natural Heritage. The sandstone formation where the two bones came from dates from the first half of the Middle Jurassic, between 180 million and 159 million years ago. This means that the bones are 5 million years older than ankylosaur remains found in Gloucestershire in 1939, making them the oldest of their kind ever discovered. As a result of Scotland’s previous connection to North America, the find suggests that stegosaurs or ankylosaurs also inhabited North America at that time. Palaeontologists working in the region have not found any Middle Jurassic bones, however, and only a few footprints from other dinosaurs. Michael Brett-Surman from the US National Museum of Natural History in Washington DC regards the discovery as key to understanding the evolution of North American dinosaurs. Brett-Surman has been studying Middle Jurassic tracks in Wyoming, but has not found any bones. “Because the Middle Jurassic faunas are so rare, any good bone is like drugs to a palaeo-junkie,” he says. Aitkin says that he saw another, larger bone in the same chunk of sandstone,