Nimravides

Nimravides is a genus of extinct saber-toothed cats that lived in North America during the Late Miocene, between 10.3 and 5.332 Ma. Despite its scientific name, Nimravides does not belong to the Nimravidae, but is a true cat belonging to the family Felidae.

History and taxonomy
The genus Nimravides was originally described by Kitt in 1958 for the species "Pseudaelurus" thinobates. In 1969, Dalquest described the species Pseudaelurus hibbardi. The species Machaerodus catocopis was described by Cope in 1887, based on a partial mandible from the Loup Fork Beds. The species Pseudaelurus thinobates and Pseudaelurus pedionomus were both described by James Reid MacDonald in 1948.

In 1975, Martin and Schultz reassigned Machairodus catacopsis to Nimravides and suggested that N. thinobates was a junior synonym of the former species. The species N. galiani was first described in 1981 based on fragmentary material from the Love Bone Beds in Florida. The same paper also described additional fossils of N. thinobates compared to the holotype of N. catacopsis, and concluded that N. catacopsis was best considered a nomen vanum and the material assigned to it should be considered N. thinobates.

"Pseudaelurus" pedionomus was reassigned to Nimravides in 1990 by Beaumont. In 2003, Tom Rothwell reassigned Pseudaelurus hibbardi to Nimravides. And in 2010 it was suggested that N. hibbardi was a junior synonym of Adelphailurus kansensis. In 2013, Mauricio Anton et al. suggested that N. catacopsis should be re-reassigned back to Machairodus. But this was refuted in 2022 by Jiangzuo et al..

Description
Nimravides catacopsis, one of the largest and latest species, was quite large, measuring 100 cm at the shoulder and was similar in size to a large tiger. It was also possessed of long, powerful legs and a long back. For many decades, it was also believed to be a member of the genus Machairodus, but, despite the similarities between them at first glance, based on autapomorphies in the skeleton, the two animals are too different to be classified as species of the same genus, and thus, Nimravides remains separate as its own genus within the Homotherini.

Paleobiology and paleoecology
Evidence published in November, 2022 suggests Nimravides was endemic to North America and that when the Machairodus-Amphimachairodus lineage emigrated to North America from Eurasia, differing aspects of their cranial anatomy allowed the newly arrived machairodont genera to survive a faunal change occurring during the earl-late Hemphillian stage of the Miocene Epoch some 6.5 million years ago. The analysis also determined that the Machairodus-Amphimachairodus lineage did not have a competitive edge over Nimravides, implying that neither newcomer or endemic species were superior to one another in regards to hunting adaptations.