Fig. 84. Carnassial or Sectorial Teeth of Carnivora (from
Flower).
Upper sectorial teeth of I. Felis, II. Canis, III. Ursus. 1. anterior, 2. middle, 3. posterior cusp of blade, 4. inner lobe supported on distinct root, 5. inner lobe posterior in position and without distinct root, characteristic of the Ursidae.
Lower sectorial teeth. 1. Felis, 2. Canis, 3. Herpestes. 1. anterior, 2. posterior lobe of blade, 3. inner tubercle, 4. heel.]
Carnivora have the teeth rooted and markedly diphyodont and heterodont. The canines are greatly developed, and the incisors are small.
In Carnivora vera the incisors are almost always 3/3. The fourth upper premolar and first lower molar are differentiated as carnassial teeth (see p. 436), and retain fundamentally the same characters throughout the suborder. The upper carnassial (fig. 84, I. II. III.) consists of a more or less compressed, commonly trilobed blade borne on two roots, with an inner tubercle borne on a third root. The lower carnassial has only two roots; its crown consists of a bilobed blade with generally an inner cusp, and a heel or talon (fig. 84, 4) behind the blade.
The most thoroughly carnivorous type of dentition is seen in the Æluroidea, and especially in the cat tribe (Felidae). In the genus Felis the dental formula is i 3/3 c 1/1 pm 3/2 m 1/1, total 30. The incisors are very small, so as not to interfere with the action of the large canines, the lower carnassial is reduced to simply the bilobed blade (fig. 84, IV), and the cheek teeth are greatly subordinated to the carnassial. The extinct Machaerodus has the upper canines comparable in size to those of the Walrus.
The Civets and Hyaenas have a dentition allying them closely to the cats. The hyaena-like Proteles has, however, the grinding teeth greatly reduced.
In the Cynoidea[163] the general dentition is i 3/3 c 1/1 pm 4/4 m 2/3, total 42. This differs from the regular mammalian dentition only in the absence of the last upper molar. The upper carnassial tooth (fig. 84, II.) consists of a larger middle and smaller posterior lobe with hardly any trace of an anterior lobe. The lower carnassial (fig. 84, V.) is typical, consisting of a bilobed blade with inner cusp and posterior talon.