Thylacosmilidae

Thylacosmilidae Temporal range: Miocene–Pliocene PreЄ Є O S D C P T J K Pg N
Thylacosmilus skull
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Infraclass:	Metatheria
Order:	Sparassodonta
Family:	Thylacosmilidae Riggs, 1933
genera
Anachlysictis Goin, 1997 Patagosmilus Forasiepi & Carlini, 2010 Thylacosmilus Riggs, 1933
Synonyms
Thylacosmilinae Riggs, 1933

Thylacosmilinae Riggs, 1933

Thylacosmilidae is an extinct family of metatherian predators, related to the modern marsupials, which lived in South America between the Miocene and Pliocene periods. Like other South American mammalian predators that lived prior to the Great American Biotic Interchange, these animals belonged to the order Sparassodonta, which occupied the ecological niche of many eutherian mammals of the order Carnivora from other continents. The family's most notable feature are the elongated, laterally flattened fangs, which is a remarkable evolutionary convergence with other saber-toothed mammals like Barbourofelis and Smilodon.

The family Thylacosmilidae was originally erected by Riggs in 1933, to accommodate Thylacosmilus, found in Pliocene strata of Argentina. Later, the family was demoted to a subfamily, as Thylacosmilinae, within Borhyaenidae, a group of superficially canid-like sparassodonts, under the assumption that Thylacosmilus was merely a late and specialized borhyaenid. Later, with the discovery of fragmentary specimens of new sparassodonts related to Thylacosmilus from Miocene and Pliocene strata, Thylacosmilidae was promoted back to familial status.

In 1997, a second genus and species of thylacosmilid was described from Miocene-aged materials found in Colombia: Anachlysictis gracilis. This animal, less specialized than Thylacosmilus, was the first indication that the family origins dates back to before the end of Miocene. In fact, the anatomy of Anachlysictis' molar teeth suggests a closer relationship with basal sparassodonts like Hondadelphys than with advanced sparassodonts like Borhyaena. Also, additional materials of a small predatory sparassodont of Colombia have been found, which has certain features diagnostic of thylacosmilids, but much less specialized, as well as indeterminate remains in Uruguay and the Argentinean Patagonia, from the early Pliocene, has been tentatively assigned to family. Forasiepi and Carlini in 2010 unveiled a third genus and species: Patagosmilus goini, also from Argentina from the mid-Miocene, with characteristics intermediate between Anachlysictis and Thylacosmilus.