Mapusaurus (Earth Lizard) was a giant carnosaurian dinosaur from the Middle-Late Cretaceous of what is now Argentina. Once thought to be a relatively small 10.2 meter long carcharodontosaurid (the estimates were based off the subadult holotype specimen), accurate estimates of the largest individual show the sizes of 43 feet (12.7 meters). Mapusaurus was excavated between 1997 and 2001, by the Argentinian-Canadian Dinosaur Project, from an exposure of the Huincul Formation at Canadon de Gato. It was described and named by paleontologists Rodolfo Coria and Phil Currie in 2006.
The type species, Mapusaurus roseae, is named for both the rose-colored rocks, in which the fossils were found and for Rose Letwin, who sponsored the expeditions which recovered these fossils.
Classification
Analysis carried out by Coria and Currie definitively showed that Mapusaurus is nested within the Carcharodontosauridae family. The authors noted that the structure of the femur suggests a closer relationship with Giganotosaurus than either taxon shares with Carcharodontosaurus. They created a new monophyletic taxon based on this relationship, the subfamily Giganotosaurinae, defined as all carcharodontosaurids closer to Giganotosaurus and Mapusaurus than to Carcharodontosaurus. They tentatively included the genus Tyrannotitan in this new subfamily, pending publication of more detailed descriptions of the known specimens of that form.
Paleobiology

Size compared to a human, based on the largest fragmentary specimen

Paleontologist Rodolfo Coria, of the Museo Carmen Funes, contrary to his published article, repeated in a press-conference earlier suggestions that this congregation of fossil bones may indicate that Mapusaurus hunted in groups and worked together to take down large prey, such as the immense sauropod Argentinosaurus. If so, this would be the first substantial evidence of gregarious behavior by large theropods other than Gigantosaurus. Although whether they might have hunted in organized packs (as wolves do) or simply attacked in a mob, is unknown. The authors interpreted the depositional environment of the Huincul Formation at the Canadon de Gato locality as a freshwater paleochannel deposit, "laid down by an ephemeral or seasonal stream in a region with arid or semi-arid climate".This bone bed is especially interesting, in light of the overall scarcity of fossilized bone within the Huincul Formation.
But given the fact an adult Sauropod is almost impossible to hunt for an alone Mapusaurus; packs/groups like Wolf packs is Much more Possible.
Technical description and diagnosis
The designated holotype for the genus and type species, Mapusaurus roseae, is an isolated right nasal (MCF-PVPH-108.1, Museo Carmen Funes, Paleontología de Vertebrados, Plaza Huincul, Neuquén). Twelve paratypes have been designated, based on additional isolated skeletal elements. Taken together, the many individual elements recovered from the Mapusaurus bone bed represent most of the skeleton.
Coria and Currie diagnosed Mapusaurus as follows: "Mapusaurus n. gen. is a carcharodontosaurid theropod whose skull differs from Giganotosaurus in having thick, rugose unfused nasals that are narrower anterior to the nasal/maxilla/lacrimal junction; larger extension of the antorbital fossa onto maxilla; smaller maxillary fenestra; wider bar (interfenestral strut) between antorbital and maxillary fenestrae; lower, flatter lacrimal horn; transversely wider prefrontal
Reconstructed skulls of adult and juvenile
Mapusaurus - Planet Dinosaur - Episode 5 - BBC One