Innominate Bone (Fragment)
Flat Bone; appendicular skeleton (part of the pelvic girdle)
Also known as: Hip Bone, Pelvic Bone, or Haunch Bone
Classification
Flat Bone; appendicular skeleton (part of the pelvic girdle)
Dimensions
In large mammals, this bone is broad and plate-like. While whole specimens can be several inches to over a foot wide depending on the species, fragments typically show a noticeable curve and varying thickness, often thinning into a blade-like edge.
Key Features
Look for a distinct 'scooped' or flared saucer-like shape. The texture often transitions from a thick, rugged area near the socket to a much thinner, smoother flat section. Even in fragments, the bone usually shows a gentle twist or organic curvature rather than being perfectly flat like a piece of slate.
Similar Bones
Often confused with the Scapula (Shoulder Blade). To tell them apart, look at the edges; the shoulder blade is usually flatter and more triangular, whereas a hip fragment will often have more dramatic curves and thicker, more irregular ridges where it once met the spine or the opposite hip.
Across Species
The hip bone’s shape is a map of an animal's movement. In humans, it is short and bowl-shaped to support upright walking. In four-legged animals like deer or cattle, it is much longer and more rectangular to accommodate powerful running muscles. In birds, these bones are fused into a light, rigid structure called a synsacrum to provide a stable base for flight.
Evolutionary History
This bone evolved from the simple pelvic fins of ancient fish. As early tetrapods moved onto land, the pelvis grew larger and stronger to support the weight of the body against gravity. Over millions of years, the three separate bones of the hip fused into a single sturdy unit to better transmit force from the back legs to the spine.
Photography Tips
Place the bone on a plain, contrasting surface and include a common object like a coin or ruler for size reference. Take one photo directly from above to show the overall outline, and a second photo from a side angle to capture the thickness and unique curves of the bone.