acrania a·cra·ni·a (ā-krā'nē-ə, ə-krā'-)
Congenital absence of all or a part of the skull.
Hence we may call it after the acrania as well as after the Tangles.
It is absent as a distinct gland in the acrania and Cyclostomata.
The skull-less animal lancelet, which is still living, affords a faint idea of the members of this group (acrania).