Homotherium

Homotherium is a machairodontine saber-toothed cat genus that lived approximately 3 million to 10,000 years ago in North America, Eurasia and Africa. It first became extinct in Africa some 1.5 million years ago. In Eurasia it survived until about 30,000 years ago. The last scimitar cat survived in North America until 10,000 years ago.

Anatomy
Homotherium reached 1,1 m at the shoulder and was therefore about the size of a lion. Compared to some other machairodonts, like Smilodon or Megantereon, Homotherium had relatively shorter upper canines, but they were flat, serrated and longer than those of any living cat. Incisors and lower canines formed a powerful puncturing and gripping device. Among living cats, only the tiger (Panthera tigris) has such large incisors, which aid in lifting and carrying prey. The molars of Homotherium were rather weak and not adapted for bone crushing. The skull was longer than in Smilodon and had a well-developed crest, where muscles were attached to power the lower jaw. This jaw had down-turned forward flanges to protect the scimitars. Its large canine teeth were crenulated and designed for slashing rather than purely stabbing.

It had the general appereance of a cat, but some of its physical characteristics are rather unusual for a large cat. The limb proportions of Homotherium gave it a hyena-like appearance. The forelegs were elongated, while the hind quarters were rather squat with feet perhaps partially plantigrade, causing the back to slope towards the short tail. Features of the hindlimbs indicate that this cat was moderately capable of leaping. The pelvic region, including the sacral vertebrae, were bear-like, as was the short tail composed of 13 vertebrae — about half the number in long-tailed cats.

The unusually large, square nasal opening, like that of the cheetah (Acinonyx jubatus), presumably allowed quicker oxygen intake, which aided in rapid running and in cooling the brain. As in the cheetah, too, the brain's visual cortex was large and complex, emphasizing the scimitar cat's ability to see well and function in the day, rather than the night, as in most cats.

Range and species
Homotherium probably derived from Machairodus. During the Pleistocene it occurred in vast parts of Eurasia, North America and until the middle pleistocene (about 1.5 million years) even in Africa. Homotherium survived in Eurasia until about 30,000, in North America even until 10,000 years ago.

Several species (nestianus, sainzelli, creantidens, nihowanensis, ultimum) are recognized from Eurasia, which differ mainly in the shape of the canines and in body size. But facing the fluctuation range of the size of modern large cats, it is highly probable, that all belong to just one species, Homotherium latidens.

Two species described form the early Pleistocene of Africa are Homotherium ethiopicum and Homotherium hadarensis. But they also differ hardly from the Eurasian forms. On the African continent the genus dissapeared about 1,5 million years ago. In North America, a very similar species, Homotherium serum occurred from the latest Pliocene until the latest Pleistocene. Their relicts were found at various sites between Alaska and Texas. In the southern parts of its range the American Homotherium occurred beneath Smilodon, in the northern parts it was the only species of saber toothed cats. The american Homotherium was originally described under the name Dinobastis.

Despite Homotheriums vast range and the large amount of fossil remains from Eurasia, Africa and North America, complete skeletons of this cat are relatively rare. One of the most famous sites of Homotherium remains is the Friesenhahn cave in Texas, where 30 Homotherium were found, besides hundreds of young mammoths and several dire wolves.

Diet and habitat


The Friesenhahn cave in Texas contained the remains of over 30 Homotherium, which were discovered along with the remains of between 300 and 400 juvenile American mammoths (Mammuthus columbii). Besides mammoth, there where found only very few other potential prey species in the cave. Therefore it is unlikely that Homotherium carried carcasses of already dead animals in the cave. Such a specialism of prey in species and age structure is not covenant with a scavenging lifestyle. Because of the same reason it is also very unlikely, that the dire wolves carried the mammoths into the cave.

The worldwide association of Homotherium species with proboscideans (elephants and mastodons) and rhino remains, mainly those of juveniles, suggests that Homotherium preyed selectively on these tough-skinned animals and probably hunted in packs, carrying away the large animals it brought down. The decline of Homotherium could be due to the dissapereance of large herbivorous mammals like mammoths in America at the end of the Pleistocene. In North America fossil remains of Homotherium are less abundant than those of its contemporary Smilodon. For the most part it probably inhabited higher latitudes and altitudes, and therefore was likely to be well adapted to the colder conditions of the mammoth steppe environment.

The suggested large prey species, make it probable, that Homotherium hunted in packs. Reduced claws, relatively slender limbs and the sloping back indicate adaptions for endurance running in open habitats.