Thoracic Vertebra (Transverse Costal Facet)
Irregular bone, part of the axial (core) skeleton
Also known as: Backbone segment (rib connection point)
Classification
Irregular bone, part of the axial (core) skeleton
Dimensions
Medium-sized backbone segments, notably deeper from front to back than those in the neck, with long sloping projections extending from the rear.
Key Features
Look for a heart-shaped central body and a long, downward-slanting tail. The blue-highlighted areas are smooth, shallow pits located on the side ‘wings’ where a rib would tuck in and rest.
Similar Bones
Can be confused with neck bones or lower back bones. Identify these by looking for the small circular ‘cups’ or smooth flat spots on the sides where ribs attach; neck bones have holes for blood vessels, and lower back bones lack rib attachment spots and are much bulkier.
Across Species
In mammals, these bones act as the anchors for the rib cage. In creatures like bison or giraffes, the upward-pointing spines of these bones are exceptionally long to provide leverage for heavy neck muscles. In contrast, birds have many of these segments fused together to create a rigid platform for flight.
Evolutionary History
These structures evolved from simple support rods in early fish to complex interlocking blocks in land-dwelling tetrapods. The specific blue-highlighted areas represent the specialized meeting points where ribs evolved to hinge against the spine, allowing the chest to expand and contract for more efficient breathing on land.
Photography Tips
Capture the bone from the side to show the angle of the tail and the smooth pits where the ribs connect. Placing a coin or a ruler next to it helps viewers understand the scale of the chest cavity it once supported.
Notes
What is the blue part of this bone?