when was it discovered?
1984
Amargasaurus
 The only known skeleton was discovered in 1984 and is virtually complete, including a fragmentary skull, making "Amargasaurus" one of the best-known sauropods of its epoch. 
what is amargasaurus? A genus of sauropod dinosaur
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Amargasaurus [SEP] Introduction
Amargasaurus (; "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 is virtually complete, including a fragmentary skull, making "Amargasaurus" one of the best-known sauropods of its epoch. "Amargasaurus" was first described in 1991 and contains a single known species, Amargasaurus cazaui. It was a large animal, but small for a sauropod, reaching in length. Most distinctively, it sported two parallel rows of tall spines down its neck and back, taller than in any other known sauropod. In life, these spines most likely could have stuck out of the body as solitary structures that supported a keratinous sheath.