Amargasaurus (/əˌmɑːrɡəˈsɔːrəs/; "La Amarga lizard") is a genus of sauropod dinosaur from the Early Cretaceous epoch (129.4–122.46 mya) of what is now Argentina. The only known skeleton was discovered in 1984 and described in 1991, forming the holotype specimen of the single species Amargasaurus cazaui. The skeleton is nearly complete, including a fragmentary skull, making Amargasaurus one of the best-known sauropods from the Early Cretaceous. Amargasaurus was small for a sauropod, reaching 9 to 10 meters (30 to 33 feet) in length. It sported two parallel rows of tall spines down its neck and back, taller than in any other known sauropod. It is unclear how these spines appeared in life—they could have supported skin sails or stuck out of the body as solitary structures supporting a keratin