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 proportionally
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 result in a steeply inclined trunk, making the
overall body shape reminiscent of a modern giraffe. Also, while the
tail is a typical long dinosaur tail, it was relatively short for a
sauropod.
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. 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 30 feet off of the
ground.