Promegantereon is one of the oldest known true saber-toothed cats. Its fossils were discovered in Cerro de los Batallones, a Late Miocene fossil site near Madrid, Spain. However, it was only known from skull fragments from Eppelsheim until the early 1990s when the Cerro de los Battlones fossil beds were discovered. The animal was about high at the shoulder, similar to a leopard in size, but with a more supple body. The shape of its limbs suggests that it may have been an agile, scansorial climber, and could have hunted relatively large prey thanks to its elongate, flattened upper canines. In appearance it was highly similar to the contemporary Paramachairodus, so much so, they were and are often considered to be the same genus. However, due to its more primitive morphology as evidenced by Salesa et al. in 2002 with an in-depth description of its anatomy, Promegantereon ogygia is believed to be its own genus and species and therefore should remain separate from Paramachairodus.
