Discovered high in the Atlas Mountains of Morocco in 1999, Atlasaurus was a specialized sauropod genus from the mid-Jurassic. Estimated at about 50ft (15m) long and weighing 15 tons.

The position of Atlasaurus on the sauropod family tree hasn't been completely settled: Some have considered it a eusauropod, while others count it among the more primitive macronarians, one of the two main branches of the advanced sauropod (Neosauropoda) clade, along with diplidocoids. An earlier line of thinking pegged Atlasaurus as a close relative of the bigger, better-known Brachiosaurus, but more recent classifications place the genus among a hodgepodge group of basal titanosaurs, the macronarian line that, in the Cretaceous, produced the largest known sauropods also known as the somphospondyls.

Atlasaurus had an unusually short-necked, high-shouldered profile that represents a variation on sauropod adaptations for elevated foraging. The species claims the proportionately longest limbs of any sauropod known, likely compensating for the comparatively modest neck length to allow for mid to high-level treetop browsing. Atlasaurus's skull is also quite large and robust relative to its size.