Home >> Science & Nature >> Animals & Science

Four Types of Teeth Found in Mammals

The long-snouted spinner dolphin, with its 252 teeth, boasts the most teeth of all mammals. Mammalian teeth take on a variety of forms and functions. Certain kinds of teeth feature more prominently in the jaw, according to what the animal eats. Some mammals, such as whales, have teeth that are relatively uniform in shape; while others, like the anteater, lack teeth whatsoever. Based on a mammal's dental formula -- which provides the number of each type of tooth in the animal's jaw -- biologists can glean information about an animal's diet, trace its evolutionary history and even pinpoint the exact species to which it belongs.

Characteristics of Mammalian Teeth
- Reptiles are homodonts; meaning, their teeth all have the same shape.
  
  Mammals are heterodonts, possessing varying combinations of four types of teeth. When the jaws of a mammal clamp shut, the teeth fit perfectly together, a concept unique to mammals called occlusion. In reptiles and fish, teeth form rows and quickly wear down; other teeth move forward in the jaw to replace damaged or lost ones. Mammalian teeth, which are sturdier than reptile or fish teeth, are replaced only once in an organism's lifetime. The mouths of young mammals accommodate a limited number and size of teeth; adult teeth gradually replace many of the juvenile "milk teeth" as the individual grows.
Incisors
- The woolly mammoth's tusks are modified incisors.
  
  The incisors lie toward the front of the mouth. The teeth are flattened and possess a cutting edge designed to slice food. The tusks of elephants and the extinct mammoths and mastodons are actually incisors that never stop growing. The narwhal, a type of sea mammal related to whales and dolphins, has a left incisor that grows straight and long while its right incisor remains short; the incisors of females do not protrude at all. Lemurs use their incisors for grooming fur.
Canines
- A mouse has no canine teeth.
  
  Canines, designed to tear, usually constitute the most lengthy and pointiest of all teeth. These teeth lie beside the incisors; humans have two canines on top and two on the bottom. If present, a canine lies in each of the four sections of the mouth called quadrants. Rodents have no canines. Male animals of some pig species and primates such as baboons have pronounced canine teeth possibly used when fighting for mates or territory. Warthogs and wild pigs have curved canines that extend upwards to lengths of 10 inches or more.
Premolars
- Premolars look like a mix between canines and molars. Mammals often have several premolars sitting adjacent to one another, with the front ones resembling canines and the back premolars looking more like molars. Carnassials, specialized premolars only present in true predatory mammals, rip chunks of meat into smaller pieces. The shape of the last premolars depends on the constitution of the mammal's diet; premolars with jagged edges feature in more carnivorous, or meat, diets, whereas those with flatter surfaces are used for crushing shells or grinding vegetation. In marine mammals -- such as dolphins and whales -- whose diets consist mainly of elusive fish, premolars resemble the inward-pointing, conical teeth of frogs and alligators that grasp and hold prey.
Molars
- Unlike other teeth, molars cannot be replaced. Generally, molars have flattened surfaces for grinding; however, in carnivorous mammals, molars resemble canines. Molars do little work in carnivores, whereas in herbivores, or plant eaters, molars have reached their epitome, becoming highly specialized for grinding plant parts. The earliest mammals had molars much like those of humans because they had omnivorous diets, dining on both plant and animal life.

Animals & Science