A Giganotosaurus carolinii, one of the contenders for the world’s largest carnivorous dinosaur, was discovered in Argentina by Ruben Carolini, an auto mechanic and amateur fossil hunter. Although this dinosaur had a similar appearance to Tyrannosaurus rex—it was slightly larger than Tyrannosaurus rex but had a much smaller brain (the size and shape of a banana)—paleontologists don’t think the two were related.

The skeletal remains of a group of Giganotosaurus were discovered in Neuquen, a southern province of Argentina. There were bones of four or five of these Cretaceous period theropods; two were very large and the others smaller. Paleontologists believe this discovery is the most important evidence to date of a social, pack-hunting behavior on the part of large carnivorous dinosaurs. Approximately 90 million years ago, when these animals died, this region was similar to the present-day pampas of northern Argentina. The climate was warm and rainy, and the land was essentially low scrub, dotted with araucaria trees. After the group of Giganotosaurus died, a west-flowing river swept their bodies away. A local goat-herder found the deposit containing the dinosaur bones in an area that is now a sandy rise in a desert.