Dental formula, lower jaw, and skull views of a coyote
Dental Formula: 3, 1, 4, 2 3, 1, 4, 3 Incisors - knife-edged for biting and cutting. Canines - pointed for puncturing and tearing. Upper Jaw: Incisors, Canines, Premolars, Molars Premolars (bicuspids) - have two points for shearing and shredding. Lower Jaw: Incisors, Canines, Premolars, Molars Molars - flattened for grinding and crushing. Some Questions to Ask … 1. Do eyes (orbits) face forward (predator) or to the side (prey)? 2. Is there a big gap (diastema) between the incisors/canines and the rest of the teeth (if yes – herbivore)? 3. Is the jaw joint at the same level as the teeth (carnivore/omnivore) or is the jaw joint well above the level of the teeth (herbivore)? ↑Carnivore (Cat) vs Herbivore (Deer) 4. Is it a long face with well-retracted nasals (some herbivores) or a ↓Carnivore (Dog) vs Herbivore (Goat) short face (some carnivores)?
Keying Skulls … before you start • Different books use different terms Rostrum • Get a feel for how the animal made its living by looking at placement of eyes, teeth, etc. • How big is the skull? Wide? Long? • What is the dental formula? • Often skulls or jaws are broken, with missing Zygomatic Arch teeth – remember that skulls are symmetrical. • Smaller rodents are particularly hard to identify • Look at range maps, know who is in your area. • Remember that age plays a role in what you see (milk teeth versus permanent teeth, sutures on brain case, etc.)
Prepared by Gwen Heistand for ACR Education Sources/Diagrams: Pacific Coast Mammals by Russo & Olhausen; Animal Skulls by Richard S. White, Jr.; A Key-Guide to Mammal Skulls and Lower Jaws by Roest; Illustrated Key to Skulls of Genera of North American Land Mammals by Jones & Manning Some skulls you may find (by order) Dog family (Canidae) Order Carnivora (and a human skull)
Cat family (Felinidae)
coyote bobcat mountain lion grey fox
Raccoon family (Procyonidae) Skunk family (Mephitidae) Weasel family (Mustelidae)
long-tailed weasel striped skunk raccoon Rodent Order (Rodentia) Human 2,1,2,3 2,1,2,3
pocket gopher dusky-footed woodrat
Sonoma chipmunk grey squirrel Deer order (Artiodactyla) Bat order (Chiroptera) Rabbit order (Lagomorph)
mule deer bat brush rabbit Order Marsupialia Moles & Shrews order (Insectivora)
If you find a small skull, without a diastema and with red-tipped teeth – you have the skull of a shrew. The shrew in our area is Trowbridge’s Shrew. (The enamel of the tips of their teeth is reddish due to iron pigment. The iron deposits serve to harden the enamel and are concentrated in those parts of the broad-footed mole teeth most subject to wear.) Virginia opossum