page_title: Thylacosmilus
section_title: Description
hierarchical_section_title: Thylacosmilus / Description
caption_attribution_description: English: List by color (shoulder height in brackets) Black: Machaeroides eothen (25 cm) from the Machaeroidinae. Pink: Lycaenops ornatus (40 cm) from the Gorgonopsia. Green: Hoplophoneus occidentalis (60 cm) from the Nimravidae. Orange: Thylacosmilus atrox (60 cm) from the Thylacosmilidae. Light blue: Barbourofelis fricki (90 cm) from the Barbourofelidae. Red: Inostrancevia alexandri (110 cm) from the Gorgonopsia. Yellow: Smilodon fatalis (110 cm) from the Machairodontinae (different from Machaeroidinae). Purple: Homotherium serum (110 cm) from the Machairodontinae (different from Machaeroidinae).
context_page_description: Thylacosmilus is an extinct genus of saber-toothed metatherian mammals that inhabited South America from the Late Miocene to Pliocene epochs. Though Thylacosmilus looks similar to the "saber-toothed cats", it was not a felid, like the well-known North American Smilodon, but a sparassodont, a group closely related to marsupials, and only superficially resembled other saber-toothed mammals due to convergent evolution. A 2005 study found that the bite forces of Thylacosmilus and Smilodon were low, which indicates the killing-techniques of saber-toothed animals differed from those of extant species. Remains of Thylacosmilus have been found primarily in Catamarca, Entre Ríos, and La Pampa Provinces in northern Argentina.
context_section_description: Body mass for sparassodonts is difficult to estimate, since these animals have relatively large heads in proportion to their bodies, leading to overestimations, particularly when compared with skulls of modern members of Carnivora, which have different locomotory and functional adaptations, or with those of the recent predatory marsupials, which do not exceed 30 kg of body mass. Recent methods, like Ercoli and Prevosti's (2011) linear regressions on postcranial elements that directly support the body's weight (such as tibiae, humeri and ulnae), comparing Thylacosmilus to both extinct and modern carnivorans and metatherians, suggest that it weighed between 80 to 120 kilograms (180 to 260 lb), with one estimate suggesting up to 150 kg (330 lb), about the same size as a modern jaguar. The differences in weight estimations may be due to the individual size variation of the specimens studied in each analysis, as well as the different samples and methods used. In any case, the weight estimations are consistent for terrestrial species that are generalists or have some degree of cursoriality. A weight in this range would make Thylacosmilus one of the largest known carnivorous metatherians.
caption: Size (orange) compared to that of a human and other predators
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