Brachiosaurus

Brachiosaurus is a genus of sauropod dinosaurs that lived during the Late Jurassic, about 154 to 150 million years ago. It is notable for its proportions, including forelimbs longer than the hindlimbs and a long neck held high, with a relatively small skull. The name means “arm lizard,” referring to its elongated front limbs.

The type species, Brachiosaurus altithorax, was named by Elmer S. Riggs in 1903 from fossils found in the Morrison Formation of Colorado, USA. A second species from Africa, Brachiosaurus brancai, was described by Werner Janensch in 1914 from the Tendaguru beds of Tanzania; most later work regards that material as belonging to its own genus, Giraffatitan, though some sources still refer to it as Brachiosaurus brancai.

In terms of anatomy, Brachiosaurus was a gigantic, quadrupedal herbivore with a long neck and tail. The forelimbs were longer than the hindlimbs, contributing to an elevated shoulder height. The skull was relatively small compared with the size of the body, and the skeleton carried air sacs typical of sauropods. Length estimates commonly place mature individuals in the range of 20 to 25 meters, with body masses tens of tons.

Classification within Brachiosauridae places Brachiosaurus among the macronarian sauropods. Its fossils come from North America (Morrison Formation) and Africa, illustrating a wide geographic distribution during the Late Jurassic. Brachiosaurus is often discussed alongside related brachiosaurs and the reclassified Giraffatitan, which helps clarify sauropod diversity and evolution in this group.