Machairodontinae

Machairodontinae (from Ancient Greek μάχαιρα machaira, a type of Ancient Greek sword and ὀδόντος odontos meaning tooth) is an extinct subfamily of carnivoran mammals of the cat family Felidae, representing the earliest diverging major branch of the family.

Machairodonts varied in size from comparable to lynxes to exceeding that of lions. The Machairodontinae contain many of the extinct predators commonly known as "saber-toothed cats", including those with greatly elongated upper maxillary canines, such as the famed genus Smilodon and Megantereon, though the degree of elongation was variable, and in some machairodontines like Dinofelis the length of the upper canines was much more modest. Sometimes, other carnivorous mammals with elongated teeth are also called saber-toothed cats, although they do not belong to the felids. Besides the machairodonts, other saber-toothed predators also arose in the nimravids, barbourofelids, machaeroidines, hyaenodonts and even in two groups of metatherians (the thylacosmilid sparassodonts and the deltatheroideans). Unlike living big cats, which generally clamp the muzzle or throat of prey to asphyxiate them, saber-toothed machairodontines are thought to have killed prey using a bite to the neck once immobilised, using their neck muscles to drive the saber teeth into the throat while the lower jaw served as an anchor, causing rapid death via blood loss.

Likely originating in Eurasia during the Middle Miocene, they eventually spread to every continent except Australia and Antarctica. Machairodonts were the dominant group of cats and large mammalian predators across Afro-Eurasia and North America during the late Miocene and Early Pliocene, a time when the ancestors of living cats (Felinae sensu lato) were mostly small sized. Machairodonts began to decline during the Pleistocene, perhaps as a result of environmental change and consequential changes in prey abundance, competition with large living cat lineages such as the pantherins as well as possibly archaic humans. The last species belonging to the genera Smilodon and Homotherium became extinct along with many other large mammals around 12-10,000 years ago as part of the end-Pleistocene extinction event, following human arrival to the Americas at the end of the Late Pleistocene.