Dental and Skull Anatomy of Carnivores, Herbivores, and Omnivores

An animal’s diet is one of the most important aspects of its biology, and it helps shape the behavior, evolution, and anatomy of the species. The development and arrangement of an animal’s teeth, known as its dentition, reflects this best; but an animal’s skull evolves to suit its diet as well. In general, meat-eating carnivores have teeth for tearing and skulls capable of biting with great force, while the plant-eating herbivores have teeth and skulls equipped to grind tough vegetation. Omnivores, which eat both plants and animals, have skulls and dentition suitable for a wide range of foods. These trends are so strong that paleontologists can often determine the diet of an extinct animal from nothing more than a few teeth or skull fragments.

Carnivores

Carnivorous animals subsist on the flesh, bones, and viscera of other creatures. Most carnivores have long, sharp teeth adapted to ripping, tearing or cutting flesh. While many also possess a few molars in the back of their mouths, and sharp incisors in the front, the most important teeth for carnivores are their long, sharp canine teeth. Carnivores drive these teeth through the flesh of their prey with the help of very large temporalis muscles, which are responsible for pulling the lower jaw upwards and backwards towards the skull. The temporalis muscles attach to the jaw at one end, and the top of the skull at the other end. To help accommodate larger temporalis muscles, some predators have evolved to have an enlarged ridge, termed the sagittal crest that acts as an attachment point or anchor for the muscle. However, the sagittal crest is not exclusively limited to carnivores, as it also appears in many herbivorous primates as well. Additionally, because predators must capture and kill their food before they can eat it, some possess teeth that aid in prey capture. Cats, for example, use their four, long canine teeth to sever their prey’s spinal cord. Some snakes have even more specialized prey-capturing teeth that have evolved into hypodermic-needlelike fangs to deliver venom into their prey.

Herbivores

Herbivores survive by consuming plant material. While some are indiscriminate grazers that consume a variety of plants, others are specialists that only eat a single plant species. For example, goats may eat virtually any vegetation they encounter, but koalas subsist entirely on eucalyptus plants. In general, plant foods are difficult to breakdown and digest; so, many herbivores have several pairs of broad molars that they use to grind leaves, shoots, and twigs. Often, herbivores feature ridged molars and jaws capable of moving sideways. Both of these traits help herbivores to grind their food more effectively. Most herbivores are missing canines entirely, and those that do possess them usually have very small or reduced canines that are not very important for chewing food. Some herbivores have large incisors for clipping or tearing vegetation, but they may only occur on the lower jaw. For example, most deer lack upper incisors and press their lower incisors against their hard, upper palate to rip twigs and branches from trees. By contrast, horses have both upper and lower incisors that they use to clip vegetation cleanly. Some herbivores have evolved teeth that are no longer involved in feeding at all. For example, the large tusks of elephants are highly modified incisors. Elephants use their tusks to manipulate items in their environment, dig for water, and defend themselves. Walruses and some pigs also feature incisors that have evolved into tusks used for foraging, defense, and intra-species combat.

Omnivores

Omnivores, such as raccoons, opossums, bears, and humans, are animals that consume both plant and animal material. Accordingly, omnivores have dentition, skulls, and teeth suitable for handling a variety of foods. Most omnivores have evolved different types of teeth, located in different parts of their mouths. In such scenarios, each type of tooth excels at handling a different type of food. For example, humans use their incisors and canines for ripping and cutting, and their molars and premolars for grinding. Biologists describe animals with such teeth as having heterodont dentition. By contrast, the teeth of homodont animals, such as iguanas, are all the same shape. As with some carnivores that have teeth to aid in prey capture, some omnivores have teeth that help them to obtain, rather than process, their food. Rodents are famous for their long, continuously growing incisors, which they use to chew through husks, shells and wood. This allows them to access well-protected or difficult-to-access foods, such as nuts. Although rodents are omnivores that occasionally eat insects and scavenge carcasses, plant material makes up the bulk of their diet. Their dentition reflects this as well: Rodents have strong molars, yet lack canine teeth entirely. Instead, rodents have a gap between their incisors and molars, termed a diastema.

References

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