Based on previously reported hybridizations, cats have long been considered to belong to a single basic type.1 0However, there has been discussion concerning whether great cats and small cats might represent independent sister clades. Recent DNA sequencing data confirm that such distinctions are not fundamental in nature and that all cats share a common genetic ancestry. More recently described hybridizations between great cats and small cats, along with various other studies described in the present article, further support the hypothesis that all cats belong to a single clearly delineated basic type. The Nimravidae (paleosabers), the Machairodontinae (neosabers) and the genus Panthera, each underwent a prominent radiation during the tertiary period. All three taxa represent cat-like placental carnivores, and they may all have arisen from the same basic type.
Cats and their taxonomic position
The cat family is placed within the order Carnivora, which comprises nine extant families (or ten if mongooses are considered a separate family; Herpestidae). The carnivores are grouped into two suborders: the catlike carnivores, or Feliformia, including the Felidae (cats), the Hyaenidae (hyenas), the Viveridae (civets), and the Herpestidae (mongooses); and the dog-like carnivores, or Caniformia, including the Canidae (dogs), the Ursidae (bears), the Procyonidae (raccoons), and the Mustelidae (weasels), as well as two marine families, the Otariidae (sea lions) and the Phocidae (seals). The present role of carnivores in nature is regulatory, keeping in check the numbers of herbivores. They are assumed to indirectly help maintain healthy populations of herbivores by selectively devouring non-healthy and phenotypically disadvantaged animals. The carnivores share a relatively homogeneous phenotype. Many are capable of running quickly, possess conspicuous canine teeth often used for catching and killing prey, and display the carnivore-typical carnassial teeth, which include the last premolars of the upper jaw and the first molars of the lower jaw. Instead of having a grinding surface, these teeth have a flattened, razor-like crown used for slicing through muscle tissue when devouring prey. In the omnivorous carnivores, such as bears, true carnassial teeth do not develop.
The 38 species of extant cat have a very characteristic phenotype readily distinguished from other species of animals, even by laymen. Recently, the clouded leopard (Neofelis nebulosa) was separated into two species, which, if acknowledged, brings the total number of species to 39.2 They possess a lithe, muscular, compact and deep-chested body. Technical diagnostics include: pointed, elongate canine teeth; large carnassials, strongly shearing in function; the dental formula 3/3, 1/1, 2-3/2, 1/1; ossified auditory bullae, inflated in appearance and divided by a bilaminate septum (except Leopardus jacobita, the Andean mountain cat, which has a double-chambered bulla);3 a tongue covered with numerous, horny papillae that are directed backwards; digitigrade extremities with five toes on the forefoot and four on the hindfoot; claws that are sharp, strongly curved, and usually highly retractile, protected by a fleshy sheath (except in the genus Acinonyx, the cheetahs).4