Most members of the order Carnivora can be recognized by their enlarged fourth upper premolar and first lower molar, which together form an efficient shear for cutting meat and tendon. These teeth are referred to as the carnassial pair. The exceptions are a few forms, such as bears, raccoons, and seals, in which these teeth are secondarily modified.
Besides usually having carnassials, almost all Carnivora retain the primitive number of incisors (3/3); an exception is the sea otter, which has 2/3. The outer (3rd) incisor is often relatively large and canine-like. The canines are large and conical. The number of teeth behind the carnassials varies considerably, from 1/1 in some cats to 2/2 in bears. All teeth are rooted and diphyodont.
The skulls of carnivorans are varied in form. Most have a well-defined, transverse glenoid fossa, and the dominant motion of the jaw is in the dorsal-ventral direction. The primary muscle powering the jaw is the temporal, and sagittal crest associated with the temporal is commonly a conspicuous part of the surface of the skull. Carnivores also have a strong zygomatic arch and a relatively large braincase. The auditory bullae and the turbinals also tend to be large and complex. Carnivores are fairly intelligent animals and most have relatively large brains. All members of Carnivora have simple stomachs.
Pinnipeds are large, perhaps because water conducts heat well and large animals have a low surface area to body mass ratio, which minimizes heat loss due to conduction. Their bodies are insulated by a thick layer of fat called blubber. In all species, the external ears are small or absent, the external genitalia and nipples are hidden in slits or depressions in the body, and the tail is very small. The forelimbs and hindlimbs are transformed into paddles. In both, the proximal limb elements (humerus and femur) remain within the body, and other aspects of the limbs, limb girdles, and spine are highly specialized for swimming. Most species have a relatively short rostrum, and the orbits are large. The cheek teeth are usually homodont (no differentiation along the toothrow), and the teeth are usually shaped like simple cones.
Carnivores tend to be medium-sized animals; too small and they couldn't find enough within their capacity to kill; too large and they wouldn't be able to satisfy their appetites. However, as a group, carnivores span a wide range of body sizes. Least weasels (Mustela nivalis), the smallest carnivores, can weigh as little as 35 grams, and male southern elephant seals (Mirounga leonina), the largest carnivores, can weigh more than 3,600 kg. Many carnivore species are sexually dimorphic in size. Usually males are larger than females (as with fishers, lions, and wolves) but in a few species females are larger than males (as with spotted hyenas). Additionally, males of some species have ornamentation that females lack (as is the case with the inflatable probosci of male elephant seals).
Many carnivores have thick, luxurious coats, though some, like walruses, have coats that are quite sparse. Their fur comes in various colors, including black, white, orange, yellow, red, and almost every imaginable shade of gray and brown. In addition, many carnivores are striped, spotted, blotched, banded, or otherwise boldly patterned. Some species, such as gray wolves, are polymorphic for coat color. Domesticated cats and dogs exhibit thousands of combinations of coat colors and body shapes as a result of selective breeding by humans.
Other Physical Features: endothermic ; heterothermic ; homoiothermic; bilateral symmetry ; polymorphic
Sexual Dimorphism: sexes alike; female larger; male larger; sexes shaped differently; ornamentation