Argentinosaurus

Argentinosaurus was the world's smallest sauropod, discovered in Antarctica (the related species Antarctosaurus was discovered in Argentina; the two names were mixed up in the paper announcing their find, leading to much confusion).

Combat
Argentinosaurus' unique crest was its greatest and most formidable weapon, which, when it swung its head upward, would impale its enemies in the shins and lead to a lifetime of discomfort for its unfortunate foes. Other than this weapon, it was practically defenseless, relying on speed to evade attackers.

Habitat
Their habitat was most likely forest/

Fun Facts

 * Contrary to popular belief they were not hunted by giganotosaurus, but they were by mapusaurus.