Sprint of the giant cheetah
Today the cheetah, Acinonyx jubatus is the only cat with clear adaptations for extremely fast sprint running, but in the past there were other species, more or less closely related to it, which also developed that kind of specialisation. The American cats of the genus Miracinonyx (about which I wrote in some detail in an earlier post) lived during the Pleistocene and paralleled to a remarkable degree the cursorial features of the cheetah skeleton, although none of them was quite as specialised as the true cheetah. But in the Pliocene and Pleistocene of the Old World there was an early species of the true cheetah genus Acinonyx, what we could call a cheetah with a difference. Of course I am talking about Acinonyx pardinensis, the giant cheetah known from many fossil sites from Spain to China, and which is known to have been considerably taller than the modern species. It is tempting to imagine that, having comparable adaptations for running as the modern cheetah but with absolutely longer limbs, the giant cheetah could have reached higher peak speeds, but would it?
Many years ago I had the opportunity to study casts of a partial skeleton of A. pardinensis from Perrier (France) housed at the Paris Museum of Natural History, and I was impressed by the animal’s enormous size and advanced running adaptations. The animal probably weighted about 70 kg, but its limb bones were quite elongated and so were its lumbar vertebrae, betraying a long and flexible back just as in the modern cheetah. But a detailed examination reveals some features in which the giant cheetah appears to be intermediate between the advanced morphology of the modern cheetah and that of the more “normal”, slower cats. For instance, the femur is not as strongly bowed as in A. jubatus, and the fibula is relatively robust without signs of the incipient fusion with the tibia observed in living cheetahs. In the radius, the tuber for the biceps muscle occupies about 10% of the shaft length in A. pardinensis as in most felines, while in the modern cheetah it is only half that long (muscle force tends to concentrate in the proximal part of the limb in the cheetah, as in all cursorial mammals).
More recently, the bones of the forelimb of a giant cheetah were found at the Georgian site of Dmanisi, and their study has revealed some interesting facts. The authors estimate that the body mass of that individual would be in the vicinity of 100 kilos, quite larger than the individual from France that I examined and more than twice the average weight of extant cheetahs. The humerus bone is far more stout than in modern cheetahs, probably in relation with the animal’s great mass, but otherwise the proportions of the bones are remarkably elongate.
Here is a photo of the Dmanisi giant cheetah forelimb exhibited at the National Museum of Georgia in Tbilisi (by the way, the small round objects are not cheetah bones, they are actually hyena coprolites!)
Other fossil sites, including Saint Vallier in France and Pantalla in Italy, have yielded amazing fossil skulls of A. pardinensis, showing a considerable but not total similarity with modern cheetahs. The skull was proportionally somewhat longer and lower than in A. jubatus, thus resembling more “conventional” cats. But the dentition is very similar to that of the modern cheetah, especially in the fact that the upper carnassial was remarkably blade-like, lacking the inner cusp or protocone. This feature indicates that the animal consumed little if any bone, and, just like modern cheetahs, it would hurriedly eat the more meaty parts if its prey and leave the rest for more powerful competitors.
All in all , we get a complex picture of A. pardinensis. Undoubtedly it would be an extremely fast sprint runner, but its adaptations were a little less refined than in its modern relative, which, combined with a greater body mass, almost surely implied that it would not be a faster animal, in spite of its longer legs. Once A. pardinensis made a kill, its blade-like carnassials allowed it to cut and consume skin and meat very efficiently, but it would probably not stay at the kill site long enough to consume any significant proportion of bone. And it makes sense that, in a world populated by large jaguars, sabertooths like Homotherium, giant hyenas like Pachycrocuta and packs of wolves, the elegant giant cheetah would not risk injury in a fight over a carcass. Just as in the modern cheetah, there was a price to pay for extreme sprinting efficiency. And just like its modern relative, its hunting would have been a true spectacle of nature. Ah, to see such a scene!