Thylacosmilus are jaguar-sized carnivorous metatherian marsupials which, due to convergent evolution, closely resemble Machairodonts such as Smilodon, easily recognized due to their lower jaws. unlike Machairodonts, the sabers of a Thylacosmilus never stop growing so damage to their fangs aren't as much of a drawback.

This large female, driven from her previous territory by larger predators, lives on an archipelago off the mainland's coast. Like Jaguars, thylacosmilus are avid and powerful swimmers, and able to take lives on land or in water with equal efficiency. Aside from a younger male Thylacosmilus (who she finds annoying) she's at the top the food chain in the islands, preying on the local Apidium, seals, fish and the occasional Moeritherium.