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Updated: May 14, 2025
The two small bicuspid "pre-molars" and the three large molars follow these on each side in each jaw. It is "quadri-tuberculate." In 60 per cent. of European lower jaws this is the case. But in 40 per cent. this tooth is quadri-tuberculate. In Polynesians, Chinese, Melanesians and negroes five tubercles are found on this tooth in 90 per cent. of the jaws examined.
A striking peculiarity of their dentition, one in which they differ from all other quadrupeds, consists in their having a single large pre-molar, the enamel of which is furrowed with vertical grooves, usually seven in number. Plagiaulex Becklesii, Falconer. Middle Purbeck. Right ramus of lower jaw, magnified two diameters. a. Incisor. b, c. Line of vertical fracture behind the pre-molars. pm.
But this resemblance is confined to general appearance, as in the prominence of the canines, and in the cutting shape of the molar teeth. For the teeth really differ much: thus the dog has on each side of the upper jaw four pre-molars and only two molars; while the Thylacinus has three pre-molars and four molars. The molars also differ much in the two animals in relative size and structure.
The word "molar" is often used to include the five cheek-teeth on each side of each jaw, but more strictly the anterior bicuspid teeth are called "pre-molars," and the three larger teeth behind them, which have no predecessors or representatives in the first or milk dentition, are called true molars or simply "molars" a rule we have followed here.
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