is the calcaneous an irregular bone?

Question

or is it a long bone, short bone, or flat bone?

Answer 1

Irregular

Although I guess some could argue that it is a short bone being roughly elongated.

Answer 2

FROM WIKIPEDIA:
The irregular bones are such as, from their peculiar form, cannot be grouped as long bone, short bone, flat bone or sesamoid bone. Irregular bones serve some unique purpose in the body of combining: (1) protection of nervous tissue (such as the vertebrae protect the spinal cord), (2) affording multiple anchor points for skeletal muscle attachment (as with the sacrum), and maintaining pharynx and trachea support, and tongue attachment (such as the hyoid bone).

They consist of cancellous tissue enclosed within a thin layer of compact bone.

The irregular bones are: the vertebræ, sacrum, coccyx, temporal, sphenoid, ethmoid, zygomatic, maxilla, mandible, palatine, inferior nasal concha, and hyoid.

There are five general classifications of bones: (1) Long bones, (2) Short bones, (3) Flat bones, (4) Irregular bones, and (5) Sesamoid bones.------------------------

From online medical dictionary:
calcaneus, calcaneum
the irregular quadrangular bone at the back of the tarsus. One of the two tarsal bones in the proximal row of bones of the hock joint and, because of its calcaneal tuber and the muscles attached to it, acts as a lever to extend the hock joint. Called also heel bone, os calcis, and fibular tarsal bone