borhyaenid

Borhyaenids were a group of extinct placental mammals that lived in South America from the Paleocene to the Pliocene epochs. They are often referred to as "marsupial wolves" or "marsupial sabre-tooths" due to their carnivorous diet and some superficial resemblances to canids and felids, although they were not closely related to either. Borhyaenids were diverse, with many species ranging in size from small, weasel-like creatures to large, powerful predators.

Their morphology suggests they were well-adapted for hunting. Many possessed strong jaws, sharp teeth, and robust limbs. Some species, like Thylacosmilus, had exceptionally long, blade-like canine teeth, reminiscent of sabre-toothed cats. The exact function of these specialized teeth is still debated, with theories including hunting large prey or intraspecific combat.

Fossil evidence indicates that borhyaenids occupied various ecological niches within South American ecosystems during the Cenozoic. They were among the apex predators in their environment for millions of years. The extinction of borhyaenids is thought to be linked to the Great American Interchange, when North American predators, such as canids and felids, migrated into South America after the formation of the Isthmus of Panama. These new competitors likely outcompeted the native borhyaenids, leading to their eventual demise.