Teeth

Mammals' mouths contain up to four main types of teeth: incisors, canines, premolars, and molars. This basic but incredibly flexible tool kit evolved early in the evolutionary history of mammals. Trying to describe some of the more extreme sets of teeth across the mammal world could end up sounding like the boldest of infomercials-- "they slice, they dice, they chop down trees - these teeth will probably save your life." It's all true, though...and then some.
 
Consider whales--some have teeth as big as a slice of pizza and others have none at all. Instead, those toothless whales have baleen--a hard, fringed material that hangs from each side of the roof of the mouth like vertical blinds. With some baleen more than 13 feet long, it works like an extremely efficient, gigantic sieve to capture tiny crustaceans and fish.
 
How about teeth that never stop growing? Like other rodents, beavers really need their incisors - specialized teeth at the front of your smile. Without these sharp, strong teeth, they couldn't gnaw bark to eat, or fell trees to build dams and lodges. So, as with all rodents, their chisel-sharp incisors have evolved to never stop growing.
 
And, of course, there is the Tasmanian devil. This averaged-size, endangered animal from the Australian island of Tasmania towers about 12 inches tall, yet packs the strongest bite-force for its size of any mammal.

The baleen on this gray whale works like an extremely efficient, gigantic sieve to capture tiny crustaceans and fish.
François Gohier/Photo Researchers

In order to keep up with the demands they put on their incisors (eating, felling trees), beavers have evolved these sharp teeth to never stop growing.
iStockphoto

Spotted hyenas can crack and crush bone with their powerful carnassial teeth—the last upper premolar and the first lower molar on each side of the jaw.
Juniors Bildarchiv/AGE Fotostock

The Tasmanian devil packs the strongest bite of any mammal for its body size.
Klein/Peter Arnold, Inc.

Thylacosmilus atrox – an extinct saber-toothed marsupial – protected its sharp upper teeth with bony, sheath-like projections on its lower jaw.
© Mauricio Anton

Fun Facts

• Gray whales spend the summer months in polar oceans, packing on fat by eating about 375,000 pounds (about 187 tons) of very small sea creatures. Like many other baleen-whale species, they do not eat all winter, when they migrate to warmer waters to breed.
• The long, bony projections on the lower jaw of Thylacosmilus atrox--an extinct saber-toothed South American marsupial--worked like sheaths for a sword, protecting the bladelike upper teeth when the animal's mouth was closed.
• Spotted hyenas can crack and crush bone with their powerful carnassial teeth--the last upper premolar and the first lower molar on each side of the jaw. They can also quickly consume an entire carcass--including skin and bones.