Thylacosmiliformes is an extinct clade of predatory metatherian mammals in the order Sparassodonta, related to the marsupials.

Members of this clade are known from the Miocene and Pliocene epochs of South America (Argentina, Colombia, and Uruguay).

The most notable thylacosmiliforms, such as Thylacosmilus, comprise the more exclusive family Thylacosmilidae and have prominent saber teeth.

[1] In their 2025 description of Dimartinia, Suarez et al. performed a phylogenetic analysis to determine its position and relationships among other sparassodonts.

Thylacosmilus Anachlysictis Patagosmilus UF 27881 (unnamed Honda Group sparassodont)[4] Prothylacynus Pharsophorus lacerans Eomakhaira Proborhyaenidae Borhyaenidae The analyses of Suarez et al. (2025) placed Eomakhaira as a non-thylacosmiliform borhyaenoid, contrasting with its initial description,[5] which suggested thylacosmilid affinities.