A BIT LONG IN THE TOOTH

You can tell a lot about a mammal from its teeth.  Most mammals are heterodonts (“hetero”= other and “dont” = teeth) with different types of teeth.  Our “tooth sampler” includes incisors, canines, premolars, and molars.  The presence of well-developed incisors, like a beaver, tell us that animal gnaws on plants (an herbivore).  We use our incisors to bite into an apple.  The presence of well developed canines (as in vampires) tells us the mammal is likely a meat eater (carnivore) that tears into it’s prey.  Premolars and molars are used for slicing and crushing foods.  Molars are especially good grinding surfaces.  Large, “flat surface” molars are found in animals that grind up plants (e.g. cows) and are indicative of herbivores.  These teeth types are not present in all mammals, nor are they well developed in all mammals.  Think about a deer.  Have you ever seen one with prominent canines?  Nope.  If you look at a deer jaw, you’ll notice they even have gaps where no teeth occur!  If you run your tongue over your teeth, you will find that you have incisors, canines, premolars and molars.  The presence of all these types indicates we are omnivores, eating plants and animals.

Mammalogists use dental formulas to identify different species of mammals, even from the skulls.  The dental formula is like a secret code.  The code is written as the number of teeth of each type on one half of the upper jaw over the corresponding teeth on the lower jaw.  For example, incisors 3/3 tells you the mammal has three incisors on the upper half of the jaw and three incisors on the lower half.  So, a dental formula may read incisors 3/3, canines 1/1, premolars 4/4, and molars 2/3.  Since the formula is always written like this, you can skip the words and just go 3/3, 1/1, 4/4, 2/3.  Remember in this secret code we are recording ½ of the jaw (right or left) and assuming the same teeth occur on the opposite side of the jaw.  For humans the dental formula is 2/2, 1/1, 2/2, 3/3.