Thylacosmilus atrox, an extinct saber-toothed marsupial, lived in South America during the late Miocene to Pliocene epochs. It had elongated canine teeth, a robust body, and a distinctive jaw structure adapted for powerful bites. Unlike placental saber-tooths, its marsupial lineage gave it unique reproductive adaptations.

Thylacosmilus atrox was native to South America, particularly in regions that are now Argentina and Bolivia. Fossil evidence suggests that this species existed during the Late Miocene to Pliocene epochs, approximately 9 to 3 million years ago.

Thylacosmilus atrox inhabited a range of environments that included open grasslands and forests. During the Late Miocene to Pliocene, the climate in these regions was generally warmer and more humid than it is today, with a mix of savannah-like areas and more densely vegetated regions.

Thylacosmilus atrox occupied the niche of a large predator, similar to modern-day big cats. Its ecological role was likely that of an apex predator, preying on herbivorous mammals of the period. The anatomical structure, including its saber-like canines, suggests adaptations for hunting large prey in open or semi-open habitats.