Brachiosaurus (/ˌ brækiə ˈ nice ː rəs/) is a genus of saurocan dinosaur that lived in North America during the Late Jurassic, about 154-153 million years ago. It was first described by American paleontologist Elmer S. Riggs in 1903 fossils found in the Colorado River Valley in western Colorado, United States. Riggs named the dinosaur Brachiosaurus Altithorax; The generic name is Greek for “Lizard arm “, referring to its proportionally long arms, and the specific name means “deep chest “. It is estimated that the Brachiosaurus stood between 18 and 21 meters (59 and 69 feet) for a long time; Weight estimates range from 28.3 to 58 metric tons (31.2 and 64 short tons). It had a disproportionately long neck, a small skull, and a large overall size, all of which are typical for sauropods. Atipically, the Brachiosaurus had longer anterior limbs than the posterior limbs, resulting in an abruptly inclined trunk, and a proportionally shorter tail.
Brachiosaurus is the namesake genus of the family Brachiosauridae, which includes a handful of other similar sauropods. The most popular representations of Brachiosaurus are actually based on Giraffatitan, a genus of braquiosaurid dinosaur from the Tendaguru Formation of Tanzania. Giraffatitan was originally described by the German paleontologist Werner Janensch in 1914 as a species of Brachiosaurus, B. Brancai, but moved to his own sex in 2009. Three other species of Brachiosaurus have been named based on fossils found in Africa and Europe; Two are no longer considered valid, and a third has become a separate genre, Lusotitan.
The type of B. Altithorax specimen remains the most complete specimen, and it is believed that some other specimens belong to the genus, making it one of the rarest sauopods of Morrison formation. It is regarded as a high browser, possibly trimming or pinching vegetation as high as 30 feet (9 meters) from the ground. Unlike other sauropods, it was not suitable for the breed in its later limbs. It has been used as an example of a dinosaur that was most likely ectopic because of its large size and the corresponding need for sufficient forage, but newer researches suggest that it was hot-blooded. Among the most emblematic and initially thought to be one of the greatest dinosaurs, Brachiosaurus has appeared in popular culture, especially in the movie 1993 Jurassic Park.