Skull (Cranium and Mandible)
Flat and Irregular bones; Axial skeleton
Also known as: Skull, Braincase, or Jawbone
Classification
Flat and Irregular bones; Axial skeleton
Dimensions
In mammals, the skull typically consists of a rounded vault for the brain and an elongated or flattened facial region. Species-specific sizes range from a few centimeters in small rodents to nearly two meters in large whales.
Key Features
Look for the large openings for the eyes (sockets), the nasal cavity in the center of the face, and the rows of teeth along the upper and lower ridges. The rounded upper section often shows wiggly lines, called sutures, where different plates of bone meet like puzzle pieces.
Similar Bones
Individual plates of a disassembled skull can be confused with other flat bones, like the shoulder blade (scapula) or hip bones (pelvis). You can distinguish skull fragments by their unique curves, the presence of tooth sockets, or the maze-like internal air chambers found in many species.
Across Species
The skull is a masterclass in adaptation. While primates often have flat faces and forward-facing eye hollows for depth perception, predators like wolves have long snouts for a keen sense of smell. Herbivores like deer feature eye sockets on the sides of the head to scan for danger, while the skulls of many birds are exceptionally lightweight and possess large openings to reduce weight for flight.
Evolutionary History
The skull emerged from simple cartilage in early fish to protect the central nervous system and house vital sensory organs like eyes and ears. Over hundreds of millions of years, the many individual plates of the skull have fused or rearranged. In the lineage leading to mammals, the lower jaw simplified from several bones into a single strong piece, while former jaw bones moved into the ear to enhance hearing.
Photography Tips
To help with identification, take a direct 'portrait' view of the face, a side profile, and a shot from above to show the overall width. Place a coin or a ruler next to the specimen for size comparison, and use soft, natural light to highlight the subtle textures and openings.