What is "rhizocephala"

Rhizocephala \Rhi`zo*ceph"a*la\, n. pl. [NL., fr. Gr. ??? root + ??? head.] (Zo["o]l.) A division of Pectostraca including saclike parasites of Crustacea. They adhere by rootlike extensions of the head. See Illusration in Appendix.

Rhizocephala are derived barnacles that parasitise decapod crustaceans. Their body plan is uniquely reduced in an extreme adaptation to their parasitic lifestyle, and makes their relationship to other barnacles unrecognisable in the adult form. The name Rhizocephala derives from the Greek roots (, "root") and (, "head"), describing the adult female, which mostly consists of a network of thread-like extensions penetrating the body of the host.