extinct genus of carnivorous marsupials (marsupial) found as fossils in deposits dated from about 10 million to 3 million years ago during the late Miocene (Miocene Epoch) and early Pliocene epochs (Pliocene Epoch) in South America. Thylacosmilus was sabre-toothed and was about as large as a modern jaguar (Panthera onca). To a remarkable degree, Thylacosmilus paralleled the evolution of sabre-toothed cats (sabre-toothed cat). Its canine teeth (canine tooth) were long and powerfully developed; they were used for stabbing prey and fit into a well-developed flange, or projecting edge, in the chin region of the lower jaw. Thylacosmilus became extinct after the land connection between North and South America was established during the middle of the Pliocene Epoch.