Brachiosaurus

Phylogeny: Dinosauria > Saurischia > Sauropodomorpha > Plateosauria > Massopoda > Sauropodiformes > Sauropoda > Gravisauria > Eusauropoda > Neosauropoda > Macronaria > Titanosauriformes > Brachiosauridae

Overview: One of the most recognizable of the sauropods, Brachiosaurus was first described as a genus in 1903 by the American paleontologist Elmer S. Riggs. He based the description on a set of partial remains discovered a few years earlier in Colorado. Recovered fossils included limb bones, vertebrae, ribs, and part of the hips. Its generic name means “arm lizard”, referring to how its front limbs were longer than its hind limbs, which at that time was quite unusual for a sauropod. Also notable for that time was its size, with it being the largest sauropod described up until that point. It was poorly known from fossils, however. This would seemingly change in 1914, when a supposed new species of Brachiosaurus was named from Tanzania; Brachiosaurus brancai. It was based on a far more complete set of remains. The general image most people have of Brachiosaurus is heavily based on this African species. Its tall, arched nasal bone and short torso are commonly pictured elements of its physique. Older artistic depictions of Brachiosaurus draw heavily from its anatomy, which is unfortunate, as Brachiosaurus brancai is no longer classified under Brachiosaurus at all.

Differences between the type species, B. altithorax, and those of B. brancai were noted as early as the 1980’s. The latter was officially recognized as a separate genus, called Giraffatitan. Some of its notable differences were its far narrower chest, shorter torso, shorter tail, and overall lighter build than that of Brachiosaurus. Definitive skull material from Brachiosaurus also showed that its nasal arch, while somewhat tall, was not as dramatic as that of Giraffatitan. The two were still relatives, being classified in the family Brachiosauridae. They were also some of the largest animals in their respective environments and were alive at around the same time. Brachiosaurus is currently only known from the Morrison Formation in the United States. It coexisted with other sauropod genera like Camarasaurus and Diplodocus, probably feeding from much taller branches than either, being able to reach up to nine meters or more in the air. While no longer the largest known dinosaur, it was still large enough to ward off most predators as an adult, which may’ve included theropods like Allosaurus or Torvosaurus. Brachiosaurus fossils, unfortunately, remain quite rare even now. Some scattered remains continue to be found, with a few suggesting some rare individuals grew to be notably larger than others.