The Thylacoleonidae are an extinct family of carnivorous vombatiform marsupials characterised by their unique dention that included a pair of secateur-like third premolars and crenulated bunodont molars. The family was present in Australia between the late Oligocene and late Pleistocene.
The family consists of five genera (Enigmaleo, Lekaneleo, Microleo, Thylacoleo and Wakaleo), and 12 species, ranging from the small (590g) early Miocene Microleo attenboroughi to the large (100-120 kg) Pleistocene hypercarnivore Thylacoleo carnifex. Wakaleo and Thylacoleo independently exhibit morphoclinal trends, which involved an increase in body size and the length of the sectorial third premolar. Simultaneously, there was a reduction and eventual loss of posterior molars.
Browse some thylacoleonid fossils: