Amphimachairodus

Amphimachairodus (from Ancient Greek ἀμφί (amphí), meaning "both", μάχαιρα (mákhaira), a type of ancient sword, and ὀδούς (odoús), meaning "tooth") is an extinct genus of homotherin machairodontine felids. It inhabited Eurasia, North America, and possibly Africa during the Late Miocene to Early Pliocene epoch. It was probably descended from Machairodus, and in turn ancestral to later homotheriins like Homotherium.

The genus Amphimachairodus was first proposed by Miklos Kretzoi for the species Machairodus palanderi.

Machairodus horribilis was first described in 1903 by Schlosser, who failed to correctly designate a holotype specimen, and thus the species was largely ignored until a 2008 paper redescribed the species and properly designated a lectotype for it. It was subsequently suggested to be reassigned to Amphimachairodus by Ruiz-Ramoni et al. (2019).

Amphimachairodus pliocaenicus was described in 1988 by Joan Pons-Moyà based on fossils from the early Pliocene, found on the Iberian Peninsula. But Ruiz-Ramoni et al. in 2019 considered the fossils too scarce to confirm its assignment to the genus.

Machairodus kurteni was described in 1992. The same paper also resurrected the previously synonymized Pogonodon copei as Machairodus copei, and reassigned the subspecies Machairodus aphanistus taracliensis as Machairodus giganteus taracliensis.

Machairodus kabir was described in 2005, and reassigned to Amphimachairodus in 2007. The describing paper also considered the species Machairodus tingii, Machairodus leoninus, Machairodus taracliensis, and Machairodus palanderi synonyms or subspecies of "Machairodus" giganteus. In 2022, this species was proposed to be reassigned to a separate genus, called Adeilosmilus.

Amphimachairodus alvarezi was described by Ruiz-Ramoni et al. in 2019.

In 2023, a review of the genus considered species Amphimachairodus irtychensis a junior synonym of A. horribilis, and A. kurteni a synonym of A. palanderi.