Carnivora (/kɑːrˈnɪvərə/kar-NIH-vər-ə) is anorder ofplacental mammals specialized primarily in eating flesh, whose members are formally referred to ascarnivorans. The order Carnivora is the sixth largest order of mammals,[22] comprising at least 279species. Carnivorans are found on every major landmass and in a variety of habitats, ranging from the coldpolar regions of Earth to the hyper-arid region of theSahara Desert and the open seas. Carnivorans exhibit a wide array of body plans, varying greatly in size and shape.
Carnivora are divided into twosuborders, theFeliformia, containing the truefelids and several"cat-like" animals; and theCaniformia, containing the truecanids and many"dog-like" animals. The feliforms include theFelidae,Viverridae,hyena, andmongoose 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 theBering land bridge. The caniforms include theCaninae,Procyonidae,bears,mustelids,skunks, andpinnipeds that occur worldwide with immense diversity in their morphology, diet, and behavior.
The oldest known carnivoran line mammals (Carnivoramorpha) appeared inNorth America 6 million years after theCretaceous–Paleogene extinction event.[24][25] These early ancestors of carnivorans would have resembled small weasel orgenet-like mammals, occupying a nocturnal shift on the forest floor or in the trees, as other groups of mammals like themesonychians and later thecreodonts were occupying the megafaunal faunivorous niche. However, following the extinction of mesonychians and theoxyaenid creodonts at the end of the Eocene, carnivorans quickly moved into this niche, with forms like thenimravids being the dominant large-bodied ambush predators during the Oligocene alongside thehyaenodont creodonts (which similarly produced larger, more open-country forms at the start of the Oligocene). By the timeMiocene 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.
Life reconstruction ofTapocyon robustus, a species ofmiacid
The order Carnivora belongs to a group of mammals known asLaurasiatheria, which also includes other groups such asbats andungulates.[26][27] Within this group the carnivorans are placed in the cladeFerae. Ferae includes the closest extant relative of carnivorans, thepangolins, as well as several extinct groups of mostlyPaleogene carnivorous placentals such as thecreodonts, thearctocyonians, andmesonychians.[28] The creodonts were originally thought of as the sister taxon to the carnivorans, perhaps even ancestral to, based on the presence of thecarnassial teeth,[29] 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,[30] and this suggests a separate evolutionary history and an order-level distinction.[31] 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.[28]
The closest stem-carnivorans are themiacoids. The miacoids include the familiesViverravidae andMiacidae, and together the Carnivora and Miacoidea form the stem-cladeCarnivoramorpha. 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).[32][33]
Carnivoramorpha as a whole first appeared in thePaleocene of North America about 60 million years ago.[25] Crown carnivorans first appeared around 42 million years ago in theMiddle Eocene.[34] Their molecular phylogeny shows the extant Carnivora are amonophyletic group, thecrown group of theCarnivoramorpha.[35] 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-likefeliforms and the dog-likecaniforms.[36] In feliforms, the auditory bullae are double-chambered, composed of two bones joined by aseptum. Caniforms have single-chambered or partially divided auditory bullae, composed of a single bone.[37] Initially, the early representatives of carnivorans were small as the creodonts (specifically, 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 thenimravids, and by theMiocene most of the extant carnivoran families have diversified and become the primary terrestrial predators in the Northern Hemisphere.
In 1758, theSwedishbotanistCarl Linnaeus placed all carnivorans known at the time into the groupFerae (not to be confused with the modern concept of Ferae which also includes pangolins) in thetenth edition of his bookSystema Naturae. He recognized six genera:Canis (canids and hyaenids),Phoca (pinnipeds),Felis (felids),Viverra (viverrids, herpestids, and mephitids),Mustela (non-badger mustelids), andUrsus (ursids, large species of mustelids, and procyonids).[19] It was not until 1821 that the English writer and travelerThomas Edward Bowdich gave the group its modern and accepted name.[2]
Initially, the modern concept of Carnivora was divided into two suborders: the terrestrialFissipedia and the marinePinnipedia.[38] Below is the classification of how the extant families were related to each other after American paleontologistGeorge Gaylord Simpson in 1945:[38]
Since then, however, the methods in which mammalogists use to assess the phylogenetic relationships among the carnivoran families has been improved with using more complicated and intensive incorporation of genetics, morphology and the fossil record. Research into Carnivora phylogeny since 1945 has foundFissipedia to be paraphyletic in respect to Pinnipedia,[39] with pinnipeds being either more closely related to bears or to weasels.[40][41][42][43][44] The small carnivoran families Viverridae,[45] Procyonidae, and Mustelidae have been found to bepolyphyletic:
Mongooses and a handful ofMalagasy endemic species are found to be in a clade with hyenas, with the Malagasy species being in their own familyEupleridae.[46][47][48]
The African palm civet is a basal cat-like carnivoran.[49]
Pandas are not procyonids nor are they a natural grouping.[51] The giant panda is a true bear[52][53] while the red panda is a distinct family.[54]
Skunks and stink badgers are placed in their own family, and are the sister group to a clade containing Ailuridae, Procyonidae and Mustelidaesensu stricto.[55][54]
Below is a table chart of the extant carnivoran families and number of extant species recognized by various authors of the first (2009[56]) and fourth (2014[57]) volumes of theHandbook of the Mammals of the World:
Skull of afossa (Cryptoprocta ferox). Note the large and conical canine andcarnassial teeth common infeliforms.
The canine teeth are usually large, conical, thick and stress resistant. All of the terrestrial species of carnivorans have threeincisors on each side of each jaw (the exception is thesea otter (Enhydra lutris) which only has two lower incisor teeth).[58] The thirdmolar has been lost. The carnassial pair is made up of the fourth upper premolar and the first lower molar teeth. Like most mammals, the dentition isheterodont, though in some species, such as theaardwolf (Proteles cristata), the teeth have been greatly reduced and the cheek teeth are specialised for eating insects. In pinnipeds, the teeth arehomodont as they have evolved to grasp or catch fish, and the cheek teeth are often lost.[59] In bears and raccoons, the carnassial pair is secondarily reduced.[59] The skulls are heavily built with a strongzygomatic arch. Often asagittal crest is present, sometimes more evident in sexually dimorphic species such assea lions andfur seals, though it has also been greatly reduced in some small carnivorans.[59] Thebraincase is enlarged with thefrontoparietal bone at the front. In most species, the eyes are at the front of the face. In caniforms, therostrum is usually long with many teeth, while in feliforms it is shorter with fewer teeth. The carnassial teeth of feliforms are generally more sectional than those of caniforms.
Ablack-backed jackal (Lupulella mesomelas) trying to predate on abrown fur seal (Arctocephalus pusillus) pup. These two species illustrate the diversity in bodyplan seen among carnivorans, especially between pinnipeds and their terrestrial relatives.
Aside from an accumulation of characteristics in the dental and cranial features, not much of their overall anatomy unites carnivorans as a group.[58] All species of carnivorans arequadrupedal and most have five digits on the front feet and four digits on the back feet. In terrestrial carnivorans, the feet have soft pads. The feet can either bedigitigrade as seen in cats, hyenas, and dogs orplantigrade as seen in bears, skunks, raccoons, weasels, civets, and mongooses. In pinnipeds, the limbs have been modified intoflippers.
Members of the Carnivora order, like thistiger, have pads on their feet.
Unlikecetaceans andsirenians, which have fully functionaltails to help them swim, pinnipeds use their limbs underwater to swim.Earless seals use their back flippers; sea lions and fur seals use their front flippers, and thewalrus uses all of its limbs. As a result, pinnipeds have significantly shorter tails than other carnivorans.
Aside from the pinnipeds, dogs, bears, hyenas, and cats all have distinct and recognizable appearances. Dogs are usuallycursorial mammals and are gracile in appearance, often relying on their teeth to hold prey; bears are much larger and rely on their physical strength to forage for food. Compared to dogs and bears, cats have longer and stronger forelimbs armed with retractableclaws to hold on to prey. Hyenas are dog-like feliforms that have sloping backs due to their front legs being longer than their hind legs. The raccoon family andred panda are small, bear-like carnivorans with long tails. The other small carnivoran familiesNandiniidae,Prionodontidae,Viverridae,Herpestidae,Eupleridae,Mephitidae, andMustelidae have throughconvergent evolution maintained the small, ancestral appearance of the miacoids, though there is some variation seen such as the robust and stout physicality ofbadgers and thewolverine (Gulo gulo).[58]
The length and density of thefur can vary depending on the environment that the species inhabits. In warm climate species, the fur is often short in length and lighter. In cold climate species, the fur is can be either dense or long, often with an oily substance that helps to retain heat. The pelage coloration differs between species, often including black, white, orange, yellow, red, and many shades of grey and brown. Some are striped, spotted, blotched, banded, or otherwise boldly patterned. There may be a correlation between habitat and color pattern; for example, spotted or banded species tend to be found in heavily forested environments.[58] Some species like the grey wolf arepolymorphic with different individual having different coat colors. Thearctic fox (Vulpes lagopus) and thestoat (Mustela erminea) have fur that changes from white and dense in the winter to brown and sparse in the summer. In pinnipeds andpolar bears, a thick insulating layer of blubber helps maintain their body temperature.
Sexual dimorphism inpinnipeds, particularlyelephant seals, is the most pronounced among Carnivorans.Sexual dimorphism inlions is the most prominent amongfelidsSexual dimorphism is the condition where sexes of the same species exhibit differentmorphological characteristics, particularly characteristics not directly involved in reproduction.[62] Sexual dimorphism in carnivorans, in which males are larger than females, is common. Sexual selection is frequently cited as the cause of the intraspecific divergence in body proportions and craniomandibular morphology between the sexes within the Carnivora order.[63][64] It is anticipated that animals withpolygynous mating systems and high levels of territoriality and solitary behavior will exhibit the highest levels of sexual size dimorphism.Pinnipeds offer an illustration for this.
Carnivorans are arguably the group of mammals of most interest to humans. Thedog is noteworthy for not only being the first species of carnivoran to bedomesticated, but also the first species of any taxon. In the last 10,000 to 12,000 years, humans have selectively bred dogs for a variety of different tasks and today there are well over 400 breeds. Thecat is another domesticated carnivoran. Many other species are popular, and they are oftencharismatic megafauna. Many civilizations have incorporated a species of carnivoran into their culture: a prominent example is thelion, viewed as a symbol of power and royalty in many societies. Yet many species such aswolves and thebig cats have been broadly hunted, resulting inextirpation in some areas. Habitat loss and human encroachment as well asclimate change have been the primary cause of many species going into decline. Four species of carnivorans have gone extinct since the 1600s:Falkland Island wolf (Dusicyon australis) in 1876; thesea mink (Neogale macrodon) in 1894; theJapanese sea lion (Zalophus japonicus) in 1951 and theCaribbean monk seal (Neomonachus tropicalis) in 1952.[24] Some species such as thered fox (Vulpes vulpes) andstoat (Mustela erminea) have been introduced toAustralasia and have caused many native species to become endangered or even extinct.[65]
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