Nimravidae

Nimravidae is an extinct family of carnivorans, sometimes known as false saber-toothed cats, whose fossils are found in North America and Eurasia. Not considered to belong to the true cats, the nimravids are generally considered closely related and classified as a distinct family in the suborder Feliformia. Fossils have been dated from the Middle Eocene through the Late Miocene epochs, spanning about 33.2 million years.

Characteristics
Most nimravids had muscular, low-slung, catlike bodies, with shorter legs and tails than are typical of cats. The middle ear of true cats is housed in an external structure called an auditory bulla, which separated by a septum into two chambers.