Cryptobranch dorids constitute the most diverse group of dorid nudibranchs. The morphology of this group is relatively conserved. The major synapomorphy of this clade is the ability to retract the gill inside the pocket. However, members of the Phyllidiidae have lost the dorsal gill secondarily. In the Porostomata the radula has been lost. All cryptobranch dorids are sponge feeders.