The Family of Cats—Delineation of the Feline Basic Type1 Barnabas Pendragon and Niko Winkler
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Papers The family of cats—delineation of the feline basic type1 Barnabas Pendragon and Niko Winkler Based on previously reported hybridizations, cats have long been considered to belong to a single basic type.2 However, 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 with numerous, horny papillae that are directed backwards; digitigrade extremities with fi ve toes on the forefoot and he cat family is placed within the order Carnivora, four on the hindfoot; claws that are sharp, strongly curved, which comprises nine extant families (or ten if T and usually highly retractile, protected by a fl eshy sheath mongooses are considered a separate family; Herpestidae). (except in the genus Acinonyx, the cheetahs).4 The carnivores are grouped into two suborders: the cat- like carnivores, or Feliformia, including the Felidae (cats), One or two family histories? the Hyaenidae (hyenas), the Viveridae (civets), and the Herpestidae (mongooses); and the dog-like carnivores, The earliest cat-like carnivore family, the Nimravidae or Caniformia, including the Canidae (dogs), the Ursidae (paleosabers), includes two lineages that suddenly appear (bears), the Procyonidae (raccoons), and the Mustelidae in the late Eocene jungles of North America. One lineage, (weasels), as well as two marine families, the Otariidae represented by Hoplophoneus, was saber-toothed; the other (sea lions) and the Phocidae (seals). The present role of lineage, represented by Dinictis, was rather like a modern carnivores in nature is regulatory, keeping in check the serval. So convincingly cat-like are these fossils that numbers of herbivores. They are assumed to indirectly help originally they were called paleofelids and designated the maintain healthy populations of herbivores by selectively fi rst cats.5 The more recent cat family, the Felidae, include the devouring non-healthy and phenotypically disadvantaged modern cats, Felinae; and the neosabers, Machairodontinae, animals. The carnivores share a relatively homogeneous e.g. Smilodon.6 The Nimravidae and the Felidae display phenotype. Many are capable of running quickly, possess only modest skeletal differences. Nevertheless, they are conspicuous canine teeth often used for catching and killing placed into two distinct families. The most prominent prey, and display the carnivore-typical carnassial teeth, skeletal difference is that nimravid fossils lack a bony wall which include the last premolars of the upper jaw and the (septum) in their middle-ear chambers (auditory bullae) or fi rst molars of the lower jaw. Instead of having a grinding sometimes the whole chamber, implying these structures surface, these teeth have a fl attened, razor-like crown used were cartilaginous.7 The nimravid, Barbourofelis, which for slicing through muscle tissue when devouring prey. In lived contemporaneously with the Felidae, had ossifi ed the omnivorous carnivores, such as bears, true carnassial auditory bullae, but there is no evidence of a bony septum.8 teeth do not develop. Such morphogenetic differences require modest selective The 38 species of extant cat have a very characteristic change. Indeed even in extant cats the auditory bullae are phenotype readily distinguished from other species of fi rst cartilaginous and only later ossify. As versatile as animals, even by laymen. Recently, the clouded leopard ossifi cation of the auditory bullae has proven to be in helping (Neofelis nebulosa) was separated into two species, which, defi ne extant cat species, calling an extinct animal a non-cat if acknowledged, brings the total number of species to 39.3 that is otherwise clearly a cat, simply for want of evidence They possess a lithe, muscular, compact and deep-chested of such ossifi cation, seems excessive. body. Technical diagnostics include: pointed, elongate The Nimravidae-Felidae ‘two-family’ hypothesis is canine teeth; large carnassials, strongly shearing in function; supported less by ossifi cations and more by phylogenetic the dental formula 3/3, 1/1, 2-3/2, 1/1; ossifi ed auditory considerations; specifi cally, that the Felidae arose from bullae, infl ated in appearance and divided by a bilaminate Proailurus during the Miocene in the Old World.8 septum (except Leopardus jacobita, the Andean mountain Proailurus, the animal currently nominated the fi rst ‘true’ cat, which has a double-chambered bulla);4 a tongue covered cat, was short, only 15 cm in length. It had very many 118 JOURNAL OF CREATION 25(2) 2011 Papers civet-like features and was probably plantigrade (walking on the soles of its feet) and not digitigrade (walking on its toes) like cats today.9 Perhaps the need for a link to a postulated ‘common-civet ancestor’ is the primary motivation for trying to classify Proailurus among the cats. It had been previously classifi ed among the civets (Viverridae) and there is much to support this classifi cation still; plantigrade gait, fl atter skull, extra teeth, the bones of Proailurus are very similar to the living viverrid, Cryptoprocta, the fossa of Madagascar.2,5,7 The next most recent cat, Pseudaelurus, had a clearly cat-like skull, based on its general morphology and dentition. It roamed Europe and North American during the Miocene. Several different forms of Pseudaelurus existed and these are believed to have formed the basis for the later radiation and diversifi cation of the neofelid cats and the sabretooth tigers.9 Proailurus, from the Miocene, is the reason why New World paleosabers from the Eocene Figure 1. The anatomy of the feline hyoid apparatus and its ‘complete’ ossification. The hyoid apparatus joins the larynx (La) cannot be cats. As a result the origins of the paleosabers to the middle ear capsules (M = auditory bullae) via two parallel have had to be placed elsewhere; e.g. within the dog-like chains of seven ‘bones’. The fifth bone links the two chains, forming carnivores10 or even outside the carnivores11. It is easy to the central basihyoid. The first and seventh members of the chains see how the two-family hypothesis could be specious, based are always cartilaginous and are not displayed in the figure. Tr = trachea. (After Dahm in Peters and Hast, ref. 13.) on preconceived notions. Differences in ossifi cation of skeletal features are not were replaced by woodland savannas.15 These more necessarily diagnostic of family status. A case in point is the open forest conditions resulted in adaptive radiations in early attempt to separate small cats and big cats into separate herbivore groups including oreodonts, anchitheres and small subfamilies based on ossifi cations in their hyoid apparatus rhinocerotoids (Janis 1998). Since these were the principle and their ability to roar.7 Sir Richard Owen12 was the fi rst prey of the Nimravidae, adaptive radiation in the herbivores to explore hyoid anatomy and felid vocalization. The hyoid would account for the adaptive radiation observed in the apparatus consists of two chains of seven bones, joined paleosabers during that period. Similarly, at the Miocene/ at the fi fth (basihyoid). These stretch from the auditory Pliocene transition, grassland savannas were replaced by bullae to the larynx, support the voice box, and confer prairies.15 Adaptive radiations of cursorial herbivore groups, characteristic vocalizations (see fi gure 1). In small cats (the including camelids, antilocaprines, and equines was then felines) the third bones (epihyoids) are ossifi ed and short, accompanied by adaptive radiation of their predators, the and they cannot roar. In the larger big cats (the pantherines) Felidae.16 Today both the paleosabers (Nimravidae) and the third epihyoids are cartilaginous and extended, and all neosabers (Machairodontinae) are completely extinct. but one of these cats can roar. In snow leopards (P. uncia; Only in the extant clouded leopard (Neofelis nebulosa) can fi gure 2) the epihyoids are cartilaginous; however, they still a vestige of the saber tooth phenotype still be observed; cannot roar because they lack additional pads in their vocal although both the upper and the lower canines are folds.13,14 Ossifi cation of the seven hyoid bones in felids is pronounced, this is a unique occurrence in the cat family. never complete. Both the fi rst (tympanohyoid) and seventh Why these animals became extinct is something of a (chondrohyoid) ‘bones’ are cartilaginous. These attach to mystery. These large carnivores would have required large the auditory bullae and cartilaginous larynx, respectively.13 prey; saber teeth are ineffi cient for capturing and killing Bone ossifi cations are of less taxonomic importance than small prey. Biome change may have led to an imbalance genetic and hybridization data, which support the conclusion in predator–prey relations, resulting both in the loss of that small cats and big cats belong in the same subfamily. sustainable populations of large prey and in the extinction It is submitted that lack of ossifi cation of the auditory of these remarkable cats. bullae in the Nimravidae is similarly of questionable diagnostic use for the family’s phylogenetic position Pelage pattern—a common origin and that the Nimravidae represent at least a sister clade of the Felidae, if not actual members of the same basic The development of melanistic coat colour patterns type. Their distributions refl ected the dominant biomes. within the cat family is not entirely understood, but some During the course of the Tertiary period, gradual cooling interesting conclusions can be drawn.