Temporal Bone
Irregular Bone, part of the axial skeleton (core)
Also known as: Temple Bone
Classification
Irregular Bone, part of the axial skeleton (core)
Dimensions
In most mammals, this is a moderate-sized, highly complex structure that makes up the lower side and base of the cranium.
Key Features
It is recognized by its complex, multi-part shape. Look for the flat, shell-like plate on the top side, a sturdy horizontal arch that reaches forward to form the cheekbone, and a bony tube-like opening for the ear canal. On the underside, it features a rounded bump behind the ear and a sharp, needle-like projection pointing downward.
Similar Bones
From the side, the flat upper portion may be confused with the parietal bone, but the parietal bone sits higher up on the top of the head and lacks an ear opening or a cheek arch. The sphenoid bone is also nearby, but it is located further forward toward the eye socket and has a distinct 'butterfly' shape when viewed in its entirety.
Across Species
The temporal bone is a marvel of evolutionary engineering, housing the delicate organs of hearing and balance. In whales, these bones are incredibly dense and often detached from the rest of the skull to allow for clear underwater echolocation without interference from vibrations in the animal's own head. In many carnivores like cats and dogs, the bottom section is inflated into a hollow, bulbous shape called an auditory bulla, which acts as a resonance chamber to enhance acute hearing for hunting.
Evolutionary History
This bone is actually a fusion of several different elements that were separate in our early ancestors. In ancient fish and reptiles, the components that now make up the mammalian temporal bone were part of the jaw hinge and the back of the skull. Over millions of years, as mammals specialized their hearing, these small bones migrated and fused together to frame the ear canal and support the jaw in a new way.
Photography Tips
To capture the best identification features, take a photo directly from the side to show the ear opening and cheek arch. A second photo looking at the bottom of the skull will help highlight the complex ridges and the small pointed projections that are unique to this bone.
Notes
What is the highlighted part of the face?