Genus: Alvarezsaurus BONAPARTE, 1991
Etymology: In honor of Don Gregorio Alvarez, noted historian of Neuquen, Argentina and Greek, sauros, "lizard."
= Aluareszaurus CAI & ZHOU, 1999 (sic)

Species: calvoi BONAPARTE, 1991
Etymology: In honor of Jorge Calvo, who discovered the type.

Holotype: MUCP v 54

Locality: Northern area of Neuquen City, Neuquen Province, Patagonia, Argentina.

Horizon: Bajo de la Carpa Formation, Lower Rio Colorado Subgroup, Upper Neuquen Group.
(was Bajo de la Carpa Member, Rio Colorado Formation.)

Biostratigraphy:

Age: Coloradoan Tetrapoda Assemblage, Age: Santonian-Campanian Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.

Material: 1 fragmentary cervical, 8 articulated cervicals, 3 anterior dorsals, 2 fragmentary dorsal, 3 sacral and 13 caudal vertebrae, fragmentary scapula, coracoid, ilia, fragmentary ischia, fragmentary femora, distal end of tibia, astragalus and calcaneum, distal end of tibia, fragmentary metatarsals, phalanges 3 of digit II, 3 fragmentary metatarsals 4 phalanges of digit IV, 2 phalanges of digit III and 1 fragmentary phalange.

Note: Infraorder Alvarezsauria BONAPARTE 1991?