Giant cheetah

The giant cheetah (Acinonyx pardinensis) is an extinct species of big cat; its closest living relative is the modern cheetah.

Morphology
The lifestyle and physical characteristics of the giant cheetah were probably similar to those of its modern relative, except the giant cheetah was the height of a lion at the shoulder (but, due to its light build, it weighed considerably less than a lion). It was roughly twice the size of today's cheetahs, putting it at around 120 kg (260 lb), and about 200 cm (79 in) from head to rump, not including a 140 cm (55 in) tail. Its reconstructed shoulder height was at 90 cm (35 in). It was a specialized sprinter with long limbs just like the modern cheetah with a slightly longer back. This back was highly flexible and allowed great propulsion during a sprint.

Just as with the modern cheetah, almost every aspect of Acinonyx pardinesis was specialized for running. The muzzle is short and the nasal passage large for increased air intake during a strenuous sprint. To make room for the enlarged nasal passage, the maxilla was reduced and the anchorage for the canine roots was less, resulting in shorter canine roots and a shorter, more stout external canine, a characteristic seen in the modern cheetah. To lighten the weight of the animal, bone girth is reduced and the skeleton is lean and light, excellent for running, but not fighting or coping with injuries, severe or minor. Its thoracic cavity was consumed by large lungs and a powerful heart. The intestines were probably shorter, to lighten the animal, and muscles not used for running were reduced. The diaphragm was connected to the movement of its gait and with the stretching phase of a stride, the expansion of space in the abdominal cavity pulled the diaphragm down and forced the animal to inhale, while the contractile phase compressed the lungs and forced air out, so it had no control over its breathing while running, a commonality of most quadruped sprinters. It was a fragile animal that could be killed by a simple sprain (if it meant the individual could not run well enough to hunt). Its tail was long, probably thickly furred, and relatively heavy; it was used as a counterweight to aid in quick directional changes when chasing prey.[citation needed]

One of the most complete skulls of this species is from the well-known French site of Saint-Vallier, but the best collection of postcranial bones came from the older site of Perrier in the Massif Central, including vertebral column and long bones of one individual were found. Unfortunately, the metacarpals were not recovered, so subsequent reconstructions depict them at the same length as the modern Acinonyx.

Distribution and habitat
Giant cheetahs were present in Europe during the Early and Middle Pleistocene. The giant cheetah was found in Germany, France, and also in China and India. European cheetahs occurred alongside jaguars and leopards at some Middle Pleistocene localities, and competition among the three possibly contributed to the cheetah's decline. Its large mass and more worn claws (when compared to modern cheetahs) suggest it was less adapted to climbing, an ability that would continue to evolve until modern-day cheetahs appeared.