Thylacosmilus (Thylacosmilus Riggs, 1933)
Time period: lived in South America during the Miocene to late Pliocene epochs.
Size: Weight estimated at up to 150 kg.
Species: Thylacosmilus atrox, T.lentis
Thylacosmilus had long, saber-like upper canines and short, blunt, peg-like lower canines. The incisors were missing altogether and the other teeth were severely reduced, but, as distinct from machairodonts, their number was complete. It is estimated to have weighed around 150 kilograms. Thylacosmilus went extinct during the Pliocene, a timeframe closely corresponding to the arrival of the saber-toothed cats Smilodon and Homotherium from North America in the Great American Interchange. As such out-competition from the anatomically similar Smilodon appears to have driven the extinction, though this is unusual among other South American extinctions during the period.
Besides Proborhyaena, Thylacosmilus and the similarly sized marsupial lion(Thylacoleo carnifex) were the largest carnivorous metatherians.