A saber-toothed marsupial called Thylacosmilus atrox once stalked the South American wild, around 3.5 million years ago. This animal was like nothing alive today. Although its closest living relatives are the marsupials of Australia and the Americas, none of those species resembles Thylacosmilus in function or form.

As it hunted, Thylacosmilus would stab at its prey with its saber-like front teeth. The animal would then use powerful muscles in its neck and jaw to rip the animal apart.

The better-known Smilodon fatalis, or saber-toothed tiger, was larger. But the front teeth of the Thylacosmilus were larger in proportion to its body size than the more famous species, or any sabre-toothed species known. Thylacosmilus and Smilodon were among the five lines of saber-toothed animals which existed at the time. Unlike Thylacosmilus, Smilodons were true cats.

Computer models of both Thylacosmilus and Smilodon were created by American and Australian researchers in order to determine how the animal killed and ate its food compared to saber-toothed tigers and a modern conical-toothed cat, the leopard.

"We found that both saber-tooth species were similar in possessing weak jaw-muscle-driven bites compared to the leopard, but the mechanical performance of the saber-tooths' skulls showed that they were both well-adapted to resist forces generated by very powerful neck muscles," Stephen Wroe, research team leader, said.

The computers calculated that despite a body weight between 200 and 225 pounds, the bite of Thylacosmilus was weaker than that of a modern house cat. However, the enormous muscles in the neck of the species was able to tear prey animals to pieces, dispatching the creature for a quick meal. It is important for carnivores, then and now, to quickly kill an animal when hunting large prey. The faster the kill is made, the less chance there is that the hunter will itself be injured by its prey or be attacked by another predator.

"To achieve a kill the animal must have secured and immobilized large prey using its extremely powerful forearms, before inserting the sabre-teeth into the windpipe or major arteries of the neck - a mix of brute force and delicate precision," Wroe said.

The teeth of this pouched marsupial went so far into the back of its head, that they nearly extended into the braincase.

Results of the study into the hunting behavior of Thylacosmilus were published in the online journal PLOS ONE.