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''Brachiosaurus'' is a genus of sauropod dinosaur from the Jurassic Morrison Formation of North America. It was first described by Elmer S. Riggs in 1903 from fossils found in the Grand River Canyon (now Colorado River) of western Colorado, in the United States. Riggs named the dinosaur ''Brachiosaurus altithorax'', declaring it "the largest known dinosaur". ''Brachiosaurus'' had a disproportionately long neck, small skull, and large overall size, all of which are typical for sauropods. However, the proportions of ''Brachiosaurus'' are unlike most sauropods – the forelimbs were longer than the hindlimbs, which resulted in a steeply inclined trunk, and its tail was shorter in proportion to its neck than other sauropods of the Jurassic. ''Brachiosaurus'' is the namesake genus of the family Brachiosauridae, which includes a handful of other similar sauropods. Much of what is known by laypeople about ''Brachiosaurus'' is in fact based on ''Giraffatitan brancai'', a species of brachiosaurid dinosaur from the Tendaguru Formation of Tanzania that was originally described by German paleontologist Werner Janensch as a species of ''Brachiosaurus''. Recent research shows that the differences between the type species of ''Brachiosaurus'' and the Tendaguru material are significant enough that the African material should be placed in a separate genus. Several other potential species of ''Brachiosaurus'' have been described from Africa and Europe, but none of them are thought to belong to ''Brachiosaurus'' at this time. ''Brachiosaurus'' is one of the rarer sauropods of the Morrison Formation. The type specimen of ''B. altithorax'' is still the most complete specimen, and only a relative handful of other specimens are thought to belong to the genus. It is regarded as a high browser, probably cropping or nipping vegetation as high as possibly off of the ground. Unlike other sauropods, and its depiction in the film ''Jurassic Park'', it was unsuited for rearing on its hindlimbs. It has been used as an example of a dinosaur that was most likely ectothermic because of its large size and the corresponding need for forage, but more recent research finds it to have been warm-blooded. ==Description== Like all sauropod dinosaurs, ''Brachiosaurus'' was a quadrupedal animal with a small skull, a long neck, a large trunk with a high-ellipsoid cross section, a long, muscular tail and slender, columnar limbs.〔Upchurch, P., Barrett, P.M. & Dodson, P. (2004): "Sauropoda." Pp. 259-322 in Weishampel, D.B., Dodson, P. and Osmolska, H. (eds.): ''The Dinosauria, Second Edition''. University of California Press, Berkeley. ISBN 978-0-520-24209-8〕 The skull had a robust, wide muzzle and thick jaw bones, with spoon–shaped teeth. As in ''Giraffatitan'', there was an arch of bone over the snout and in front of the eyes that encircled the nasal opening, although this arch was not as large as in its relative.〔Foster, J. (2007). "''Brachiosaurus altithorax''." ''Jurassic West: The Dinosaurs of the Morrison Formation and Their World''. Indiana University Press. pp. 205–208.〕 Large air sacs connected to the lung system were present in the neck and trunk, invading the vertebrae and ribs, greatly reducing the overall density. Unusually for a sauropod, the forelimbs were longer than the hind limbs. The humerus (upper arm bone) of ''Brachiosaurus'' was relatively lightly built for its size, measuring in length in the type specimen. The femur (thigh bone) of the type specimen was only long.〔 Unlike other sauropods, ''Brachiosaurus'' appears to have been slightly sprawled at the shoulder joint,〔 and the ribcage was unusually deep.〔 This led to the trunk being inclined, with the front much higher than the hips, and the neck exiting the trunk at a steep angle. Overall, this shape resembles a giraffe more than any other living animal. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Brachiosaurus」の詳細全文を読む スポンサード リンク
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