Thylacosmilus

Thylacosmilus was a large cat like predator that lived in South America from the late Miocene to Early Pliocene.

Description
Thylacosmilus resembles a saber toothed cat, although it was actually a giant marsupial predator. Its teeth were longer than those of smilodon and were protected by a bony tooth gaurd, located on the lower jaw. It grew to be the size of a jaguar.

Extinction
Thylacosmilus lived until 3 million years ago, when new predators such as actual felines moved into South America. Competition between these predators may have been the reason for its extinction.