Cervical Vertebra
Irregular Bone; part of the axial (core) skeleton.
Also known as: Neck Bone, neck joint, spine segment
Classification
Irregular Bone; part of the axial (core) skeleton.
Dimensions
In mammals, these vary widely from the size of a pea in shrews to over a foot long in giraffes. They are generally wider than they are tall, featuring a large central opening for the spinal cord and smaller holes on the sides for vessels.
Key Features
Look for a distinct 'ring' or butterfly shape with a large central hollow. A defining characteristic of mammal neck bones is the presence of two small holes (channels) located on the outer wings. They often have smooth, flat surfaces where they stack against their neighbors and a small bony ridge or nub pointing toward the back.
Similar Bones
Can be confused with back bones (thoracic vertebrae), but neck bones are typically flatter and have the unique small holes on the sides which back bones lack. Back bones also usually have much longer, blade-like spikes pointing outward.
Across Species
Almost all mammals, from the tiny mouse to the towering giraffe, possess exactly seven neck bones. In giraffes, these bones are incredibly elongated to reach high foliage, whereas in whales, they are often flattened and fused together to support a rigid, streamlined body for diving. Birds, by contrast, can have many more—swans have up to 25—offering extreme flexibility.
Evolutionary History
These bones evolved from the basic spinal segments of early fish-like ancestors. As early tetrapods moved onto land, the neck region became specialized to allow the head to move independently of the shoulders, a crucial development for scanning the horizon for predators or tracking moving prey.
Photography Tips
Place the bone on a flat surface and photograph it looking directly down through the large central hole. Take a second shot from the side to show the thickness and the protrusions. Including a common object like a coin or a ruler helps show the true size.