Mammal skulls

Coyote

Use the coyote skull as an example to learn the anatomy, then find the same features on the skulls of other species.

First, you should remember some basic terms for describing bone shapes:

• Process: any bony structure that sticks out, generally forming a place for a muscle to attach.
• Fossa: an indentation in a bone. The fossa is the socket part of a ball-and-socket type joint.
• Condyle: the convex part of the joint; the ball part in a ball-and-socket joint.

Now examine these specific skull features:

• Orbit: the eye socket.
• Sagital crest: a ridge along the top of the head, formed where the parietal bones from each side meet in the middle. The sagittal crest forms an attachment point for extra-large temporalis muscles. The temporalis is one of the main muscles responsible for biting and chewing; it extends from the sagittal crest down to the coronoid process. An animal with a powerful bite is likely to have large temporalis muscles, a sagittal crest, and large coronoid processes. Many mammals do not have a sagittal crest; the muscles simply attach to the sides of the skull.
• Coronoid process: a flat structure sticking up from the mandible (lower jaw). The temporalis muscle attaches to the medial (inner) side of the coronoid process.
• Auditory bulla (also called typmanic bulla): a hard, compact structure that contains the inner ear structures.
• Occipital condyles: part of the joint between the skull and the first cervical (neck) vertebra.
• Mandible: the lower jaw bone.
• Mandibular condyle: on the mandible, the convex part of the hinge joint for the jaw.
• Mandibular fossa: on the skull, the concave part of the hinge joint for the jaw. The mandibular fossa is in the temporal bone, and the joint is called the temporomandibular joint.
• Angular process: an attachment point for the masseter muscle, which (along with the temporalis) helps in biting and chewing.
• Nuchal crest: a crest that extends laterally across the back of the skull, forming an attachment point for strong neck muscles.

More about the temporomandibular joint (TMJ): This joint functions as a hinge for the jaw. In carnivores, it's typically a tight hinge. However, in other orders, the hinge is loose. A loose TMJ allows for sideways motion of the jaw which is important for animals such as cattle and sheep, which grind sideways when chewing their food. The TMJ is loose if the mandibular condyle is open and shallow, and if the mandibular condyle moves freely within the fossa.