Carnivora ( ) is an order of placental mammals specialised primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at least 293 species. Carnivorans are found on every major landmass and in a variety of habitats, ranging from the cold polar regions of Earth to the hyper-arid region of the Sahara Desert and the open seas. Carnivorans exhibit a wide array of body plans, varying greatly in size and shape.
Carnivora are divided into two suborders, the Feliformia, containing the true felids and several animals; and the Caniformia, containing the true canids and many animals. The feliforms include the Felidae, Viverridae, hyena, and mongoose families, the majority of which live only in the Old World; cats are the only exception, occurring in the Old World and the New World, entering the Americas via the Bering land bridge. The caniforms include the Caninae, Procyonidae, bears, mustelids, skunks, and pinnipeds that occur worldwide with immense diversity in their morphology, diet, and behaviour.
Etymology The word Carnivora is derived from Latin carō (stem carn-) 'flesh' and vorāre 'to devour'.
Phylogeny The oldest known carnivoran line mammals (Carnivoramorpha) appeared in North America 6 million years after the Cretaceous–Paleogene extinction event. These early ancestors of carnivorans would have resembled small weasel or genet-like mammals, occupying a nocturnal shift on the forest floor or in the trees, as other groups of mammals like the mesonychians and later the creodonts were occupying the megafaunal faunivorous niche. However, following the extinction of mesonychians and the oxyaenid creodonts at the end of the Eocene, carnivorans quickly moved into this niche, with forms like the nimravids being the dominant large-bodied ambush predators during the Oligocene alongside the hyaenodont creodonts (which similarly produced larger, more open-country forms at the start of the Oligocene). By the time Miocene epoch appeared, most if not all of the major lineages and families of carnivorans had diversified and become the most dominant group of large terrestrial predators in Eurasia and North America, with various lineages being successful in megafaunal faunivorous niches at different intervals during the Miocene and later epochs.
Systematics Evolution
The order Carnivora belongs to a group of mammals known as Laurasiatheria, which also includes other groups such as bats and ungulates. Within this group the carnivorans are placed in the clade Ferae. Ferae includes the closest extant relative of carnivorans, the pangolins, as well as several extinct groups of mostly Paleogene carnivorous placentals such as the creodonts, the arctocyonians, and mesonychians. The creodonts were originally thought of as the sister taxon to the carnivorans, perhaps even ancestral to, based on the presence of the carnassial teeth, but the nature of the carnassial teeth is different between the two groups. In carnivorans, the carnassials are positioned near the front of the molar row, while in the creodonts, they are positioned near the back of the molar row, and this suggests a separate evolutionary history and an order-level distinction. In addition, phylogenetic analysis suggests that creodonts are more closely related to pangolins while mesonychians might be the sister group to carnivorans and their stem-relatives.
The closest stem-carnivorans are the miacoids. The miacoids include the families Viverravidae and Miacidae, and together the Carnivora and Miacoidea form the stem-clade Carnivoramorpha. The miacoids were small, genet-like carnivoramorphs that occupy a variety of niches such as terrestrial and arboreal habitats. Studies have shown that while viverravids are a monophyletic basal group, the miacids are paraphyletic with respect to Carnivora (as shown in the phylogeny below).Bryant, H.N., and M. Wolson (2004) "Phylogenetic Nomenclature of Carnivoran Mammals." First International Phylogenetic Nomenclature Meeting. Paris, Museum National d’Histoire Naturelle
Carnivoramorpha as a whole first appeared in the Paleocene of North America about 60 million years ago. Crown carnivorans first appeared around 42 million years ago in the Middle Eocene. Their molecular phylogeny shows the extant Carnivora are a monophyletic group, the crown group of the Carnivoramorpha. From there carnivorans have split into two clades based on the composition of the bony structures that surround the middle ear of the skull, the cat-like feliforms and the dog-like caniforms. In feliforms, the auditory bullae are double-chambered, composed of two bones joined by a septum. Caniforms have single-chambered or partially divided auditory bullae, composed of a single bone. Initially, the early representatives of carnivorans were small as the oxyaenids and mesonychians dominated the apex predator niches during the Eocene, but in the Oligocene, carnivorans became a dominant group of apex predators with the nimravids, and by the Miocene most of the extant carnivoran families have diversified and become the primary terrestrial predators in the Northern Hemisphere.
Classification of the extant carnivorans
In 1758, the Swedish botanist Carl Linnaeus placed all carnivorans known at the time into the group Ferae (not to be confused with the modern concept of Ferae which also includes pangolins) in the tenth edition of his book Systema Naturae. He recognised six genera: Canis (canids and hyaenids), Phoca (pinnipeds), Felis (felids), Viverra (viverrids, herpestids, and mephitids), Mustela (non-badger mustelids), and Ursus (ursids, large species of mustelids, and procyonids). It was not until 1821 that the English writer and traveller Thomas Edward Bowdich gave the group its modern and accepted name.
Initially, the modern concept of Carnivora was divided into two suborders: the terrestrial Fissipedia and the marine Pinnipedia. Below is the classification of how the extant families were related to each other after American palaeontologist George Gaylord Simpson in 1945: Order Carnivora Bowdich, 1821 Suborder Fissipedia Blumenbach, 1791 Superfamily Canoidea G. Fischer de Waldheim, 1817 Family Canidae G. Fischer de Waldheim, 1817 – dogs Family Ursidae G. Fischer de Waldheim, 1817 – bears Family Procyonidae Bonaparte, 1850 – raccoons, ringtails and coatis (also included red pandas as subfamily Ailurinae, which is now treated as a family) Family Mustelidae G. Fischer de Waldheim, 1817 – badgers, otters, weasels and skunks (as subfamily Mephitinae, now treated as family) Superfamily Feloidea G. Fischer de Waldheim, 1817 Family Viverridae J. E. Gray, 1821 – civets and allies, including mongooses (now family Herpestidae), African palm civets (now family Nandiniidae) and Asiatic linsangs (now family Prionodontidae) Family Hyaenidae J. E. Gray, 1821 – hyenas Family Felidae G. Fischer de Waldheim, 1817 – cats Suborder Pinnipedia Iliger, 1811 Family Otariidae J. E. Gray, 1825 – eared seals Family Odobenidae J. A. Allen, 1880 – walruses Family Phocidae J. E. Gray, 1821 – earless seals
Since then, however, the methods available to mammalogists to assess the phylogenetic relationships among the carnivoran families have improved, incorporating genetics, morphology and the fossil record. Research into Carnivora phylogeny since 1945 has found Fissipedia to be paraphyletic in respect to Pinnipedia, with pinnipeds being either more closely related to bears or to weasels. The small carnivoran families Viverridae, Procyonidae, and Mustelidae have been found to be polyphyletic: Mongooses and a handful of Malagasy endemic species are found to be in a clade with hyenas, with the Malagasy species being in their own family Eupleridae.Anne D. Yoder and John J. Flynn 2003: Origin of Malagasy CarnivoraYoder, A., M. Burns, S. Zehr, T. Delefosse, G. Veron, S. Goodman, J. Flynn. 2003: Single origin of Malagasy Carnivora from an African ancestor – Letters to NaturePhilippe Gaubert, W. Chris Wozencraft, Pedro Cordeiro-Estrela and Géraldine Veron. 2005 – Mosaics of Convergences and Noise in Morphological Phylogenies: What's in a Viverrid-Like Carnivoran? The African palm civet is a basal cat-like carnivoran. The linsang is more closely related to cats. Pandas are not procyonids nor are they a natural grouping. The giant panda is a true bear while the red panda is a distinct family. Skunks and stink badgers are placed in their own family, and are the sister group to a clade containing Ailuridae, Procyonidae and Mustelidae sensu stricto.
Below is a table chart of the extant carnivoran families and number of extant species recognised by various authors of the first (2009) and fourth (2014) volumes of the Handbook of the Mammals of the World: