1. how to determine the skull type using a dental formula
Ms. Manzo /17 - Wildlife Biology

2. First – an introductory handout! And some questions…
1) Why are teeth so important in studying the early evolution of mammals?
2) Define hederodont, homodont and mastication.
3) Besides eating, what are canines for?
4) What are milk teeth? How are they different from adult/permanent teeth?
5) What are occlusal surfaces?
6) Why are efficient dentitions important to animals?
7) Describe transverse jaw action. What types of animals utilize this and which don’t? Why?
8) Describe one distinctive skull feature exhibited by herbivores and related to transverse jaw action, which is reduced or absent in carnivores. (Page 18)
9) What is the dental formula for humans?

3. Animal Skull Dentition
The easiest way to begin to determine what kind of skull you are looking at is to look at the teeth of the skull.
If the teeth are present, this is easiest, though you can sometimes muddle through by looking at the skull if only the tooth sockets remain.
It's also helpful if you have both jaws available,(upper and lower mandibles) though it's not required.
Often one or the other is enough to help you figure out if the animal is an herbivore, carnivore, etc…

4. Different Types of Teeth
If you feel around your mouth with your tongue, it becomes apparent that you don't have all the same types of teeth. This is true for most animals. Teeth are specialized to do different jobs, depending on the diet of the creature (if you ever want to see a really weird skull, check out the anteater, they don't have any teeth, just a long bone snout!)
Incisors (dark blue) are at the front of the mouth and are usually for scraping or biting, so they are scoop shaped and smaller. Canines (green) are usually for ripping or tearing meat, so they are long and pointed. Premolars (pink), are behind the canines, and can be flat for grinding, like in the mouth of beavers, or they can be sharp and serrated like in dogs and canines, for tearing meat. Molars (turquoise) also vary, depending on their use. Often they are for grinding food, like in humans, but in meat eating creatures they too may be serrated and have sharp edges for ripping and tearing meat.

5. Bilateral symmetry
bilateral symmetry: All mammals, have bodies with mirror halves. The right side of the skeleton, and the external body, matches the left. For teeth, this means, that when you study the teeth of a mammal you only need to study one side of the mouth, or count teeth on one side of the skull. The other half of the jaw is exactly the same (for dental formulas you then multiply by two).
Remember that animal skulls will not always have the same number of teeth in their upper and lower jaws.
This is because each jaw may have a different function. In deer (and sheep, horses, etc.), the upper jaw has no incisors, but the lower jaw has a full set of incisors. This is because they use their lower jaw to "scoop" grass and leaves, and then the vegetation is passed to the back molars for grinding (this scooping action is what animal trackers look at to know the difference between the shearing cuts of rabbit teeth and the ragged scoop of deer teeth on vegetation).

7. Now that you know the basics, let's try to narrow down the type of animals we could be looking at: Carnivore, Herbivore, Omnivore…

8. Carnivore
Carnivores- These are true meat-eating-only animals that have sharp teeth for ripping and tearing. Often their front canine teeth are elongated and sharp and their incisors are often small and reduced in size.
Their back teeth, or molars and premolars are what we call "carnassial" meaning that they too are serrated and sharp, like the blades of a saw.
This allows them to hold, rip, and tear meat from prey.
For this classification we are also going to include insectivores like bats and some voles and moles and pescavores, or fish eaters. These creatures often have very wicked looking teeth, and sharp carnassials as well, just like the other carnivores.

9. Herbivores…
Herbivores are the plant eaters. For our purposes we will include grass, plant, and grain eaters (granivores).
Most herbivores have very flat molars and premolars in the back of their mouths (like we do) and they usually have scoop-like incisors (upper and/or lower).
In some cases, like that of rabbits, beaver and other rodents, they may have orangish curved teeth for incisors. In these creatures, the teeth are "indeterminate" and grow continually.   
This is why animals that have them (except for rabbits) are called "rodents." Rodere in Latin means to gnaw or chew. They must chew, or their teeth can grow so long that they can't open their mouths.

10. Omnivores
Omnivores eat both meat and plant material. Their teeth are usually a combination of meat eating and plant eating teeth.
If the skull has a combination of teeth then you're probably looking at an omnivore.

11. Video… https://www.youtube.com/watch?v=VejLXTsJrJc

12. Dental formulas
Each type of animal has its own unique dental formula. These formulas can be used by biologists to help accurately identify skulls and to assist in categorizing animals into families and subgroups.
A dental formula is quite simple, they just use letters to represent each type of tooth:
• I = Incisor
• C = Canine
• P = Premolar
• M = Molar
After each number you will find two numbers that look like a fraction. These aren't really fractions. The top number represents the number of a particular teeth in the top mandible (or mouth) and the bottom number represents the number of a particular type of teeth in the lower mandible or jaw.
For example, This is the dental formula of an American beaver (Castor canadensis):
American Beaver: I-1/1 C- 0/0 P- 1/1 M- 3/3= 10 x2 = 20
Notice that the total number of teeth is counted and then multiplied by two. This is because of what we mentioned earlier, bilateral symmetry. You only need to count the teeth on one side of the animal's skull and jaw, and then double it to get a full count of teeth. It simply saves you some work.

13. Feel around your mouth and determine the adult human dentition formula…
C __/___
P __/___
M___/___= ______x2= _____ total teeth

14. Also - are we carnivores, omnivores or herbivores?

15. The dentition of an adult human:
Adult Human: I - 2/2   C - 1/1   P - 2/2   M - 3/3 = 16 x 2 = 32 total teeth

16. Let us try… First, is it a carnivore, herbivore, or omnivore?
P __/___
M___/___= ______x2= _____ total teeth

17. which of the animals on the right is this skull?

18. now…. we will do this with real skulls!