Mapusaurus (indigenous/Greek for "earth lizard"); pronounced MAP-oo-SORE-us
Woodlands of South America
Middle Cretaceous (100 million years ago)
Size and Weight:
About 40 feet long and 3 tons
Large size; powerful legs and tail
The large theropod dinosaur Mapusaurus was discovered all at once, and in a big heap--an excavation in South America in 1995 that yielded hundreds of jumbled bones, which required years of work by paleontologists to sort out and analyze. It wasn't until 2006 that researchers announced the "diagnosis" of Mapusaurus, a three-ton theropod that was closely related to the even bigger Giganotosaurus and must have been one of the most feared predators of its day.
Interestingly, the fact that so many Mapusaurus bones were found jumbled together can be taken as evidence of herd, or pack, behavior--raising the possibility that this meat-eater hunted cooperatively in order to take down the huge titanosaurs populating middle Cretaceous South America. On the other hand, a flash flood could also have resulted in the accumulation of unrelated Mapusaurus bones, so the pack-hunting hypothesis should be taken with a big grain of prehistoric salt.