Sparassodonta

Sparassodonta (from Greekσπαράσσειν [sparasseing], to tear, rend; and ὀδούς, gen. ὀδόντος [odous, odontos], tooth) is an extinctorder of carnivorousmetatherianmammals related to modern marsupials. They were once considered to be true marsupials, but are now thought to be a separate side branch that split before the last common ancestor of all modern marsupials. Fossils of the order have been found exclusive to South America, although trackways suggests they were possibly present in Antarctica.

A number of these mammalian predators closely resemble placental predators that evolved separately on other continents, and are cited frequently as examples of convergent evolution. They were first described by Florentino Ameghino, from fossils found in the Santa Cruz beds of Patagonia. Sparassodonts were present throughout South America's long period of "splendid isolation" during the Cenozoic; during this time, they shared the niches for large warm-blooded predators with the flightless terror birds. Previously, it was thought that these mammals died out in the face of competition from "more competitive" placentalcarnivorans during the PlioceneGreat American Interchange, but more recent research has shown that sparassodonts died out long before eutherian carnivores arrived in South America (aside from procyonids, which sparassodonts probably did not directly compete with).

Sparassodonts have been referred to as borhyaenoids by some authors, but currently the term Borhyaenoidea refers to a restricted subgroup of sparassodonts comprising borhyaenids and their close relatives.