April 17, 2006 — -- Move over, Tyrannosaurus Rex. There's a new dinosaur in town, and he's bigger and badder than you ever were.
A ferocious meat-eater named Mapusaurus roseae and weighing almost eight tons was recently discovered in Argentina. Because the bones of several individuals were found in one place, scientists believe that the carnivores lived together in social units and hunted with deadly efficiency in well-organized packs.
Their prey? Mapusaurus probably dined on the flesh of the largest dinosaur that ever lived, Argentinosaurus, a massive 125 foot-long, 100-ton giant.
"They would have been quite formidable," said Philip Currie, paleontologist at the University of Alberta who worked on the Mapusaurus site. "These were definitely the top dogs in the Southern Hemisphere."
The Mapusaurus bones were found in a bone bed on a hill in the Patagonia region of southern Argentina. "Bone beds are a good area to work for giving info on more than one animal," said Currie, who made the Mapusaurus discovery with Rodolfo Coria of the Museo Carmen Funes in Plaza Huincul, Argentina.
Carnivorous dinosaurs like T. Rex were once believed to be solitary hunters, but new evidence suggests otherwise. Currie speculates that the Mapusaurus he and Coria discovered were all living together in a social group until their death in some catastrophic event about 100 million years ago.
"They all died together, so you can reason that they all lived together," Currie said. "Carnivores, when you find them all together like this, were probably packing animals with coordinated hunting efforts."
The group found included several younger animals about 18 feet long, who were no less dangerous than the adults. "The juveniles were faster than the adults -- they were longer-legged and more lightly built," Currie said.
Based on the remains found at the site, an adult Mapusaurus would have measured about 40 feet in length. This puts the carnivore ahead of Tyrannosaurus Rex and on par with another meat-eater, Giganotosaurus.
"Over the last decade, people have become increasingly aware of a group of gigantic meat-eating dinosaurs called carcharodontosaurids," explained Currie. This group included Mapusaurus, Giganotosaurus and other large carnivores.
It's difficult to determine the exact size of Mapusaurus, Currie explained, because the complete skeleton of a single adult has never been found. But much information can be gleaned from the skull and other bones that were uncovered at the site.
"This new animal we have is slightly larger than T. Rex, and it may be larger than Giganotosaurus," said Currie. "No matter how you cut it, this is a big animal."