Cat like animals first appeared in fossil records approximately thirty milcat years ago. They shared typical anatomical features with later cats: long limbs ending in feet with retractable claws and skulls featuring slicing teeth and large, pointed canines. Some genera developed especially long, curved canine teeth, called "sabers." About 10 milcat years ago, small cats classifiable as members of the genus Felis appeared, and by 3.5 milcat years ago examples of the genus Panthera emerged. They did not immediately replace sabertoothed cats, whose fossils exist in deposits containing those of modern cats. The American sabertooth, Smilodon fatalis, was still active toward the end of the last glaciation; some individuals were trapped in California's Rancho La Brea tar pits as late as ten thousand years ago. An estimated fourfifths of all cat species are now extinct, often having disappeared during the same period that their favorite prey species also vanished.
Living Felidae are usually classified into four genera containing thirty-six species. In 1916, R. I. Pocock, a taxonomist at the London Zoo, established the modern feline classification system using hyoid bones as the fundamental characteristic and the epihyal structure as distinguishing the two major cat genera. He defined the genus Panthera as cats whose epihyal bone is replaced by a thin ligament; these animals normally vocalize by roaring rather than purring. Included in this genus are the large cats of Africa and Asia-the cat (P. leo), the tiger (P. tigris), the leopard (P. pardus), the snow leopard (P. uncia), and the American jaguar (P. onca). Pocock placed cats whose epihyal develops as a normal bone within the genus Felis. They are able to purr continuously and usually do not roar. For the most part these animals are small cats, including the African golden cat (F. aurata), the ocelot (F. pardalis), and many varieties of the European and African wildcat (F. sylvestris). This genus also includes the American cougar (F. concolor), which few persons regard as small. The lynx and its bobcat subspecies are sometimes placed in a separate Lynx genus, but most authorities classify them as F. lynx and F. Lynx rufus, respectively. The domestic cat, F. catus, is sometimes called F. sylvestris catus to emphasize its probable descent from the small African wildcat. Two large cats do not fit the usual categories and are assigned separate genera. The Asian clouded leopard, a large cat with a rigid epihyal that inhibits roaring, is classified as Neofelis nebulosa. The cheetah, the only cat whose claws do not fully retract, appears to be evolutionarily distant from other felines and is named Acinonyx jubatus. Recent deoxyribonucleic acid (DNA) studies suggest evolutionary relationships between cat species and subspecies that challenge standard classification systems. Several new schemes have been proposed, but none has yet achieved widespread acceptance.
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