Hoplophoneus Mentalis

Although resembling a big cat, Hoplophoneus was actually one of the Nimravids, more popularly known as the ‘false sabre-toothed cats’. Nimravids were an early branch of the Carnivora and were actively hunting long before the emergence of the true cats of the Felidae. Although they looked very similar to true cats, there were many marked differences such as non-retractable claws, and lack of inner-ear bones.

Nimravids seem to have acquired many of the traits of the later sabre-toothed cats like Smilodon and Machairodus, since they also have enlarged sabre-like canine teeth in the upper jaw. Hoplophoneus also had two flanges of bone that grew downwards from the lower jaw, just as some of the other later true saber-toothed cats. These gave extra support and protection to the canines because when the mouth was closed the tips of the upper canines would not extend past the lower jaw.

The skull displayed here also has another incredible feature that is quite different in Nimravids and sets them apart from Felidae. In this amazing skull, a very nice endocast of the brain is visible. Their brain shape and lobes are quite different than those in modern cats, being more elongated, yet still very well equipped for hunting.

The relatively short bones that make up the legs of Hoplophoneus indicate that it accelerated quickly to top running speed, but would would not have been as fast as some modern cats because its legs could not cover as much ground with each stride. For this reason Hoplophoneus is believed to be an ambush hunter that would hide in the undergrowth or tall grasses, exploding out and chasing down prey animals before they had time to get away.

Seth Sorensen
www.fossilshack.com