Carnassial

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Carnassials of a dog

Carnassials are large teeth found in many carnivorous mammals, used for shearing flesh and bone in a scissor- or shear-like way. In the Carnivora, the carnassials are the modified fourth upper premolar and the first lower molar. These teeth are also referred to as sectorial teeth. [1]

Carnassial dentition[edit]

Left: Carnassial teeth of [A]bear (Ursus), [B]leopard (Panthera), [C]dog (Canis), [D]badger (Meles), and their respective close ups.
Right: Carnassial teeth of [E]otter (Lutra), [F]raccoon (Procyon), [G]mongoose (Herpestes), [H]weasel (Mustela), and their respective close-ups.
Photos taken at Imperial College London.

A defining feature of the Carnivora are their teeth, the canines and carnassials. These carnivorous mammals are diphyodont.

Carnassial teeth pairs are found on either side of the jaw, and are composed of the fourth upper pre-molar, and the first lower molar. The location these carnassial pairs is determined primarily by the masseter muscle. In this position, the carnassial teeth benefit from most of the force generated by this mastication muscle, allowing for efficient shearing and cutting of flesh, tendon and muscle.[2]

The scissor-like motion is created by the movement between the carnassial pair when the jaw closes. The inside of the fourth upper pre-molar comes into contact with the outer surface of the first lower molar, thus allowing the sharp cusps of the carnassial teeth to slice through meat.

The length and size of the carnassial teeth vary between species, taking into account factors such as:[3]

  • the size of the carnivorous animal
  • the extent to which the diet is carnivorous
  • the size of the chunk of meat that can be swallowed.

The majority of carnivorous animals have only one carnassial pair, however, marsupials have three pairs and creodonts had two.[3]

Video demonstrating the shearing action of the carnassial teeth in a otter (Lutra) jaw. Filmed at Imperial College London.
Video demonstrating the shearing action of carnassial teeth in a dog (Canis) jaw. Filmed at Imperial College London.

Evolution of carnassial teeth[edit]

A comparison of the size and shape of carnassial teeth in: [A]bear (Ursus), [B]leopard (Panthera), [C]dog (Canis), [D]badger (Meles), [E]É(Lutra), [F]raccoon (Procyon), [G]mongoose (Herpestes), [H]weasel (Mustela). Photo taken at Imperial College London.

The fossil record indicates the presence of carnassial teeth 50 million years ago, implying that Carnivora family members descend from a common ancestor. [4]

The shape and size of sectorial teeth of different carnivorous animals vary depending on diet, illustrated by the comparisons of bear (Ursus) carnassials with those of a leopard (Panthera). Bears, being omnivores, have a flattened, more blunt carnassial pair than leopards. This reflects the bear's diet, as the flattened carnassials are useful both in slicing meat and grinding up vegetation, whereas the leopard's sharp carnassial pairs are more adapted for its hypercarnivorous diet.

Disease[edit]

Wear and cracking of the carnassial teeth in a wild carnivore (e.g. a wolf or lion) may result in the death of the individual due to starvation.

Carnassial teeth infections are common in domestic dogs, and present as abscesses. Extraction of the tooth and antibiotics are necessary to ensure that no further complications occur.

References[edit]

  1. ^ Henry Fairfield Osborn (1907). Evolution of mammalian molar teeth. Macmillan. Retrieved 20 January 2011. 
  2. ^ Cope E.D. (1879). "The Origin of the Specialized Teeth of the Carnivora". The American Naturalist 13: 171–173. 
  3. ^ a b Savage R. J. G. (1977). "Evolution in carnivorous mammals". Paleontology 20: 237–271. 
  4. ^ "Carnivores". Natural History Collections. Retrieved May 2013.