Nimravides (Nimravides Kitts 1958)
Temporal range: middle Miocene- early Pliocene in North America
Dimensions: 1,7 m in length, 90 cm in height, 100 kg of weight
The fossil species assigned to the genus Machairodus were divided by Turner into two grades of evolutionary development - M. aphanistus and the North American "Nimravides" catacopis representing the more primitive grade, and M. coloradensis and M. giganteus representing the more derived grade. 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. These trends would be taken further in Homotherium, which is thought to have evolved from Machairodus.