![]() The occlusal surfaces tend to be pointed, well-suited for holding prey and tearing and shredding. Cementum is only found below the gingival line. A cap of enamel covers the crown and extends down to the neck. Ī brachydont tooth has a crown above the gingival line and a neck just below it, and at least one root. It is a type of dentition characterized by low-crowned teeth. The opposite condition to hypsodont is called brachydont or brachyodont (from brachys 'short'). The cementum and the enamel invaginate into the thick layer of dentin. The body is covered with cementum both above and below the gingival line, below which is a layer of enamel covering the entire length of the body. ![]() The occlusal surface is rough and mostly flat, adapted for crushing and grinding plant material. Hypsodont molars lack both a crown and a neck. Hypsodont molars can continue to grow throughout life, for example in some species of Arvicolinae (herbivorous rodents). Some examples of animals with hypsodont dentition are cattle and horses, all animals that feed on gritty, fibrous material. Hypsodont dentition is characterized by high-crowned teeth and enamel that extends far past the gum line, which provides extra material for wear and tear. Bunodont molars are effective crushing devices and often basically quadrate in shape. They are most common among omnivores such as pigs, bears, and humans. In bunodont molars, the cusps are low and rounded hills rather than sharp peaks. Upper and lower dentition of a chimpanzee This variant is regarded as an example of convergent evolution. Some Jurassic mammaliaforms, such as docodonts and shuotheriids, have "reversed tribosphenic" molars, in which a talonid-like structure develops towards the front of the lower molar, rather than towards the rear. For example, the dentition of the Early Cretaceous monotreme Steropodon is similar to those of Peramus and dryolestoids, which suggests that monotremes are related to some pre-tribosphenic mammals, but, on the other hand, the status of neither of these two groups is well-established. Many paleontologists argue that it developed independently in monotremes (from australosphenidans), rather than being inherited from a common ancestor that they share with marsupials and placentals (from boreosphenidans) this idea still has some critics. Tribosphenic molars were present in the direct ancestors of all three living mammal groups, but it was most likely not ancestral to mammals as a whole. The protocone of the upper molar and talonid basin of the lower molar mesh together as a crushing system similar to a mortar and pestle. The protocone cusp is on the lingual side of the tooth, while the anterior paracone and posterior metacone are on the buccal side. Upper molars look like three-pointed mountain ranges, with their features mirrored from the lower molars. Generalized tribosphenic left upper molar, showing the protocone, paracone, and metacone. Therian mammals (placentals and marsupials) are generally agreed to have evolved from an ancestor with tribosphenic cheek teeth, with three main cusps arranged in a triangle. According to the widely accepted "differentiation theory", additional cusps have arisen by budding or outgrowth from the crown, while the rivalling "concrescence theory" instead proposes that complex teeth evolved by the clustering of originally separate conical teeth. Mammalian, multicusped cheek teeth probably evolved from single-cusped teeth in synapsids, although the diversity of therapsid molar patterns and the complexity in the molars of the earliest mammals make determining how this happened impossible. Cingula are often incomplete ridges that pass around the base of the crown. Cusps are occasionally joined to form ridges and expanded to form crests. The cusps contain both dentine and enamel, whereas minor projections on the crown, called crenulations, are the result of different enamel thickness. The basic elements of the crown are the more or less conical projections called cusps and the valleys that separate them. In mammals, the crown of the molars and premolars is folded into a wide range of complex shapes.
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