covering bone

dermal bone (any of the the superficial bones in Teleostomi derived from the dermis and overlying the deeper elements of the skull. Primitive fishes have more dermal bones than higher ones, e.g. the armour of Ostracodermi. Dermal bones are a form of membrane bones, i.e. they arose directly from connective tissue membranes without the cartilaginous precursors which precede endochondral bones. They may be divided into laterosensory canal bones that develop in relation to the sensory canals, bones derived from mesenchymous tissue and anamestic bones (q.v.). Also called achondral, membrane and investing bones)