Maxilla (Fragment)
Irregular bone, flat bone; part of the axial skeleton (cranium)
Also known as: Upper jawbone, snout bone, cheekbone base
Classification
Irregular bone, flat bone; part of the axial skeleton (cranium)
Dimensions
This bone is typically thin and lightweight, forming a hollow triangle or wedge shape. In mid-sized mammals, it is often two to three inches long, characterized by a curved bottom edge housing tooth sockets and a flared upper section that forms the side of the snout.
Key Features
The most identifying feature is the row of tooth sockets or actual teeth along the bottom edge. It often features a prominent 'bridge' or arch that forms part of the cheekbone and a smooth, curved upper surface that creates the floor of the eye socket or the wall of the nasal cavity.
Similar Bones
This is most often confused with the mandible (lower jaw). You can tell them apart because the maxilla usually has a much more complex, irregular top edge where it connects to the rest of the skull, whereas the mandible is usually a simpler, hook-shaped or L-shaped bone designed for movement.
Across Species
The maxilla varies wildly based on diet. In carnivores like cats or foxes, it is short and deep to support powerful shearing teeth, whereas in grazers like deer, it is long and slender to reach grass. In many fish, the maxilla is a mobile, swinging bone that helps expand the mouth to suck in prey. In contrast, in modern birds, this bone is fused and lightweight to support the keratinous beak.
Evolutionary History
Originally appearing as part of a series of armored plates in early jawed fish, the maxilla eventually migrated inward to become the primary tooth-bearing bone of the upper face in land-dwelling vertebrates. Over millions of years, air-filled spaces developed within it to reduce the weight of the skull while maintaining structural strength for chewing.
Photography Tips
Place the bone on a flat surface with the tooth row facing downward to show its natural orientation. Take one photo directly from the side to show the profile and another looking straight down at the sockets or teeth. Using a plain background and a coin for size reference is very helpful.