Proailurus was a compact animal, just a little larger than the domestic cat, weighing about 20 lbs (9 kg). It had a long tail, large eyes and sharp claws and teeth. It was probably a tree-dweller.
One of the next known cats on the feline family tree is Pseudaelurus, which lived 20-10 million years ago. Pseudaelurus is also an ancestor of domestic and big cats. Other branches of the feline family tree originating with Proailurus gave rise to Dinofelis and Machairodus. The latter is an ancestor of Smilodon, better known as the sabertooth cat or sabertooth tiger.