The Order Carnivora represents a major and highly successful group of mammals, technically referred to as carnivorans. This biological order, placed beneath the Class Mammalia, includes a wide array of familiar animals such as cats, dogs, bears, weasels, and seals. The order is geographically widespread, inhabiting nearly every continent and ocean, and contains at least 279 species across 13 to 15 families. Although the name Carnivora is derived from the Latin for “flesh-devouring,” the classification is based on shared ancestry and physical traits, not strictly on diet.
Physical Traits Defining the Order
The defining morphological feature uniting members of the Order Carnivora is a specialized set of teeth known as the carnassial pair. This unique dental adaptation involves the fourth upper premolar and the first lower molar, which have been modified into blade-like structures. These teeth operate like shears, sliding past each other to efficiently slice and shear muscle tissue, tendon, and skin.
The skulls of carnivorans display several related features that support this powerful shearing action. They possess strong, conical canine teeth for seizing prey and a robust skull structure with a pronounced sagittal crest. This crest serves as the attachment point for the large temporalis muscle, the primary muscle responsible for the powerful up-and-down movement of the jaw.
The jaw joint, or glenoid fossa, is well-defined and transverse, which restricts lateral movement and ensures the carnassial blades meet precisely. Limb structure varies greatly among terrestrial carnivorans, ranging from the digitigrade stance of dogs and cats (walking on toes) to the plantigrade stance of bears (walking on the sole of the foot).
Classification into Suborders
The Order Carnivora is fundamentally divided into two distinct suborders, reflecting an early evolutionary split: Feliformia (cat-like) and Caniformia (dog-like). The most reliable anatomical distinction between these two groups lies in the structure of the auditory bulla, the bony capsule that encloses the middle and inner ear. Feliforms possess a double-chambered auditory bulla, which is divided by a septum of bone.
Feliformia
Feliformia includes families such as Felidae (true cats), Hyaenidae (hyenas and aardwolves), Herpestidae (mongooses), and Viverridae (civets and genets). These carnivorans tend to have shorter snouts, fewer teeth, and more highly specialized carnassial teeth for slicing meat. Feliforms are generally more specialized hunters, often exhibiting retractable or semi-retractable claws, and most are native to the Old World (Africa and Asia).
Caniformia
Caniformia, the “dog-like” carnivorans, are characterized by an auditory bulla that is single-chambered or only partially divided. This suborder is geographically more widespread and includes a greater diversity of morphology, diet, and behavior. Families include Canidae (dogs, wolves, foxes), Ursidae (bears), Mustelidae (weasels, otters, badgers), Mephitidae (skunks), and Procyonidae (raccoons).
The Caniformia also includes the aquatic pinnipeds—seals, sea lions, and walruses—which represent a highly specialized departure from their terrestrial relatives. Caniforms typically feature longer snouts and less specialized dentition compared to feliforms, reflecting their tendency toward opportunistic feeding and omnivory.
Diversity in Feeding Habits
Despite the order’s name, not all carnivorans are strict meat-eaters; their feeding habits represent a spectrum of dietary specialization. Carnivorans are classified into three major dietary categories based on the percentage of vertebrate meat in their diet.
Hypercarnivores are species whose diet consists of more than 70% meat, including all members of the cat family and the polar bear. Mesocarnivores consume 50% to 70% meat, incorporating non-vertebrate foods like insects, fruits, and plant material. This category includes species like foxes and badgers, which are effective hunters but readily incorporate other food sources.
The least carnivorous group is the hypocarnivores, which consume less than 30% meat and are sometimes considered omnivores. Hypocarnivores include animals like raccoons and most species of bears, which rely heavily on diverse plant matter and invertebrates. The most extreme example of dietary variation is the giant panda, a member of the bear family that is almost entirely herbivorous, subsisting on bamboo.
This dietary range demonstrates how the ancestral carnassial teeth have been adapted or even reduced. In bears, for instance, the carnassials are less developed, and the molars are broader and flatter for crushing plant material.