abstract
| - The Machairodontinae is an extinct subfamily of carnivoran mammals of the family Felidae. They were endemic to North America from the Pleistocene living from about 23 million until about 11,000 years ago. The Machairodontinae contain many of the extinct predators commonly known as "saber-toothed cats", including the famed genus Smilodon, as well as other cats with only minor increases in the size and length of their maxillary canines. Sometimes, other carnivorous mammals with elongated teeth are also called saber-toothed cats, although they do not belong to the felids. Besides the machairodonts, saber-toothed predators also arose in Nimravidae, Barbourofelidae, Creodonta (Machaeroidinae) and even in a group of sparassodont metatherians. Machairodonts are divided into two types: dirk-toothed and scimitar-toothed. Dirk-toothed cats had elongated, narrow upper canines and generally had stocky bodies. Scimitar-toothed cats had broader and shorter upper canines and a typically lithe body form with longer legs. The longer-toothed cats often had a bony flange that extended from their lower mandible. However, one genus, Xenosmilus, known only from two fairly complete fossils, broke this mould, possessing both the stout, heavy limbs associated with dirk-toothed cats, and the stout canines of a scimitar-toothed cat.
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