[12] The characteristics of the more advanced grade include a relative elongation of the forearm and a shortening of the lumbar region of the spine to resemble that in living pantherine cats.

[13] Modern scholarship generally classifies Machairodus as one of the most primitive members of the tribe Homotherini (with some authors retaining the name "Machairodontini" for the group[14]).

[17] M. alberdiae was contemporary with M. aphanistus in Cerro de los Batallones fossil deposits and was smaller and more primitive in anatomical features and would not have exceeded 100 kg (220 pounds).

Until its discovery, no true species representative of the genus Machairodus had been described from North America, as they had been reassigned to other genera, such as Nimravides and Amphimachairodus.

[22] Studies of Machairodus indicate that the cat relied predominantly on its neck muscles to make the killing bite applied to its victims.

There are also clear adaptations for precise movements, strength, and flexibility in the neck that show compatibility with the canine-shearing bite technique that machairodontine cats are believed to have performed.

[24] M. aphanistus fossils recovered from Batallones reveal a high percentage of tooth breakages, indicating that unlike later machairodonts, due to a lack of protruding incisors Machairodus often used its sabers to subdue prey in a manner similar to modern cats; this was a more risky strategy that virtually ensured that damage to their saber teeth often occurred.

M. aphanistus seemed to prefer open woodland habitat, as evidenced by finds at Cerro de los Batallones, which is of Vallesian age.

Large herbivores found at the Batallones site included horses like Hipparion (consumpution of Hipparion by Machairodus aphanistus is strongly supported by isotopic analysis of remains from Batallones[28]), the hornless rhinoceros Aceratherium, the giraffes Decennatherium and Birgerbohlinia, the deer Euprox and Lucentia, the antelopes Paleoreas, Tragoportax, Miotragocerus and Dorcatherium, the “gomphotherid” elephantoid Tetralophodon, the porcupine Hystrix, and the suid Microstonyx.

Machairodus would have competed for such prey with the Amphicyonid Magericyon, fellow machairodonts Promegantereon and Paramachairodus, bears such as Agriotherium and Indarctos, and the small hyaenid Protictitherium.

They would’ve coexisted with a number of other large carnivores including two unnamed species of agriotherine bears, the barbourofelid Albanosmilus, fellow Machairodont Amphimachairodus, and the huge hyena Dinocrocuta.