Saber-toothed Cats - Morphology

Morphology

These subfamilies evolved their saber-toothed characteristics entirely independently. They are most known for having maxillary canines which were, in some species, up to 50 cm (19.7 inches) long and extended down from the mouth even when the mouth was closed. Sabre-toothed cats were generally more robust than today's cats and were quite bear-like in build. They were believed to be excellent hunters and hunted animals such as sloths, mammoths, and other large prey. Evidence from the numbers found at La Brea Tar Pits suggests that Smilodon, like modern lions, was a social carnivore.

The first late saber-tooth instance is a group of animals ancestral to mammals but not yet mammals. Known as synapsids or mammal-like reptiles, they were one of the first groups of animals to experiment with specialization of teeth and many had long canines. Some had two pairs of upper canines with two jutting down from each side, but most had one pair of upper extreme canines. Because of their primitiveness, they are extremely easy to tell from machairodonts. With no cononoid process, many sharp "premolars" more like pegs than scissors, a very long, lizard-like head are among several things that mark them out.

The second appearance of long canines is Thylacosmilus. Thylacosmilus is the most unique of the saber-tooth mammals and is also easy to tell apart. It differs from machairodonts in a possessing a very prominent flange and a tooth that is triangular in cross section. The root of the canines is more prominent than in machairodonts and a true sagittal crest is absent.

The third instance of saber teeth is from order Creodonta. The small and slender Machaeroides bore canines that were thinner than in the average machairodont. Its muzzle was longer and narrower.

The fourth saber-tooth appearance is the ancient family of carnivores, the nimravids and they are notoriously hard to tell apart from machairodonts. Both groups have short skulls, tall sagittal crests, and the general skull shape is very similar. Some have distinctive flanges, some have none at all, so this confuses the matter further. Machairodonts were almost always bigger, though, and their canines were longer and more stout for the most part, but exceptions do appear.

The fifth appearance is the barbourofelids. These carnivores are very closely related to actual cats, and as such, they are hard to tell apart. The best known barbourofelid is Barbourofelis, which differs from most machairodonts by a mandible that is much heavier and more stout, smaller orbits, massive and almost knobby flanges, and canines that are farther back. The average machairodont has well-developed incisors, but barbourofelids were more extreme.

The sixth and last of the sabertooth group to evolve were the machairodonts themselves.

• 1st saber-tooth instance: Synapsida, the gorgonopsid Gorgonops skull.

• 2nd saber-tooth instance: Thylacosmilidae (Sparassodonta). Thylacosmilus atrox skull.

• 3rd Saber-tooth Instance: Creodonta, family undetermined. Machaeroides skull.

• 4th saber-tooth instance: Nimravidae (Carnivora). Hoplophoneus primaevus skull and upper cervical vertebrae.

• 5th saber-tooth instance: Barbourofelidae (Carnivora). Barbourofelis skeleton.

• 6th saber-tooth instance: Felidae (Carnivora). Smilodon skull and upper cervical vertebrae.