Vertebra
Irregular bone, part of the core axial skeleton
Also known as: Backbone, spinal segment, spool bone
Classification
Irregular bone, part of the core axial skeleton
Dimensions
Varies immensely depending on the animal, ranging from tiny discs in small rodents to broad, sturdy blocks in large mammals and massive cylindrical wheels in whales.
Key Features
Look for a central spool-like body, a ring-shaped opening where the spinal cord passes through, and various bony wings or fins projecting outward for muscle attachment.
Similar Bones
Can sometimes be confused with small round wrist or ankle bones, but vertebrae are easily distinguished by their hollow central ring and distinct projecting fins.
Across Species
Vertebrae show incredible diversity across the animal kingdom. In fish, they are simple hourglass shapes designed for side-to-side swimming. In birds, they allow for extreme flexibility of the neck. In large land mammals like elephants, they feature towering top spines to anchor heavy back muscles.
Evolutionary History
Spinal segments evolved very early in vertebrate history, replacing the continuous flexible rod called the notochord with a segmented chain of bony protectors that shield the main nerve cord while allowing graceful bending and twisting.
Photography Tips
Photograph from the top to show the central ring opening, and take a second side-profile shot to capture the height and projecting bumps. Include a coin or ruler for scale, and use soft, angled lighting to highlight the textured surface.