Acinonyx pardinensis

Acinonyx pardinensis Temporal range: Early to Middle
Skull, Firenze
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Family:	Felidae
Genus:	Acinonyx
Species:	A. pardinensis
Binomial name
Acinonyx pardinensis Croizet & Joubart, 1828

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

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 79.37–100 kg (175.0–220.5 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). Like the modern cheetah, the giant cheetah was likely a sprinter, but based on its proportions, was probably slower than the modern cheetah species.

Just as with the modern cheetah, almost every aspect of Acinonyx pardinesis was specialized for running, though not as fast. 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. As evidenced by Marco Cherin, Denis Geraads et al, the giant cheetah may have also had a stronger bite than modern cheetahs, perhaps enough to crush bone. To lighten the weight of the animal, bone girth is reduced and the skeleton is lean and light, excellent for running, but probably not for 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 likely 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. Analysis of its skeleton indicates that the giant cheetah was intermediate in morphology between the swift-moving cheetahs and slower big cats; for one, its head was more proportionate to that of the cheetah's cougar-like ancestors in appearance and its limbs were relatively more robust than the modern cheetah. Indeed, the giant cheetah may have less resembled its modern cousin and instead have had more in common in regards to morphology with the modern snow leopard, whose skeletal proportions are very similar. Despite its longer legs and potential as a sprinter, the giant cheetah was overall less suited to speed than its modern relatives due to its intermediate build and greater mass

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