Vertebrae and Ribs (Thoracic Segment)
Irregular and flat bones, part of the axial skeleton
Also known as: Backbone and Rib Cage Section
Classification
Irregular and flat bones, part of the axial skeleton
Dimensions
Varies widely by species, ranging from a few inches in small mammals to several feet in large ungulates. This section shows a series of interlocking central blocks with long, slender curved bones attached along the sides.
Key Features
Look for a central column of stacked, interlocking blocks featuring upward-pointing spines, with long, curved, blade-like bones extending outward from the sides to form a protective basket shape.
Similar Bones
Can be confused with individual detached ribs or fragments of the skull, but the presence of a central jointed column clearly identifies it as a spinal segment.
Across Species
In mammals, the mid-back region anchors a sturdy cage of ribs that protects the vital organs. Birds have fused and lightweight variations for flight, while snakes possess dozens of identical, highly flexible segments without a distinct rib cage split.
Evolutionary History
The backbone is an ancient design originating in early fish ancestors over 500 million years ago, evolving from a simple flexible rod into a segmented chain of bony blocks that allowed animals to move efficiently onto land.
Photography Tips
Photograph from directly above to capture the full curve of the attached ribs and the alignment of the central column. Include a coin or ruler for scale, and use soft, even lighting to show the intricate textures of the bone joints.