Scapula

It is a large, flat triangular bone with two basic surfaces, The posterior (dorsal) and the costal (anterior, or ventral). there are three borders that meet in three angles. The scapula articulates with the clavicle and the humerus.

The anterior (front) side of the scapula shows the fossa subscapularis (subscapular fossa) to which the subscapularis muscle attaches.
The posterior surface of the scapula is divided by a bony projection, the spina scapulae (opposite to the fossa subscapularis) into the supraspinous fossa and the infraspinous fossa. This projection is called the spine of the scapulae. It begins flat at the base of the shoulder bone, ascends in distal direction for all animals but carnivores and humans to its peak at about the middle of the scapula, this peak is called tuber scapulae. After this peak the spina scapulae steeply decays in height. For humans and carnivores and bovinae the spina runs into a forward pointing hook called acromion, which continues past the main part of the bone.
Another hook-like projection comes off the lateral angle of the scapula, and is called the coracoid process. The end of this hook is the site of attachment of many muscles, such as the coracobrachialis muscle.
Near the base of the coracoid process, so also on the lateral angle, there is a depression called the glenoid cavity. This forms the socket that the head of the humerus articulates with.

When fragmentary, the scapula might be mistaken for the pelvis. In all of its flat part, how ever the scapula is thinner than the pelvis. Indeed the scapular blade is mostly a single, thin layer of bone instead of spongy bone sandwiched between cortices as in the pelvis.

The fragment of scapular balde or infant scapulas could be mistaken for wings of the sphenoid, but the thin bone of the scapula is bounded by broken surfaces whereas broken sphenoid pieces normally have free or sutural edges.