Atlasaurus

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

Overview: With a length of about fifteen meters, Atlasaurus wasn’t an overly large sauropod, but it was fairly tall. This was due in part to its limb anatomy, with its front legs being longer than its hind limbs, giving it an upwardly inclined back up towards its relatively short neck. Atlasaurus had a fairly large skull – at least proportionately for a sauropod – that was boxy in shape with a tall nasal arch. Its teeth were thick and chisel-like in form, implying it could consume tough plant matter. Like most of the sauropods, Atlasaurus probably didn’t do much chewing, with most food processing going on in the gut, aided by swallowed stones called gastrolithes. Potential food included conifers and cycads, though plants may’ve been more limited during dry seasons. Atlasaurus fossils are known from the Guettioua Formation, in what is now Morocco. Described in 1999, the genus derives its name from Morocco’s Atlas Mountains and, by extension, the titan Atlas from Greek myth.

Atlasaurus is based on what is basically a complete skeleton, first discovered in the early 1980’s. It seems to represent an adult animal. Given so much of its body is known, one might expect there is little debate surrounding this genus, but that’s unfortunately not the case. Atlasaurus had a mix of traits making it harder to classify among other sauropods. Originally, the genus was referred to the family Cetiosauridae, but later studies proved this was probably not accurate. Its limb anatomy and skull was similar to that of Brachiosaurus and its kin, so it may’ve been a brachiosaurid. Other studies have suggested Atlasaurus was a member of the eusauropod clade Turiasauria, or that it was a more generalized basal eusauropod. Studies done on turiasaurs in recent years, however, have actually found some support for it being a brachiosaurid instead, or at least a member of the larger clade Macronaria, so Atlasaurus was probably at least a member of the Neosauropoda.