Phyllodesmium is a genus of predatory sea slugs, aeolid nudibranchs, marine gastropod mollusks in the family Facelinidae.These nudibranchs occur in the tropical Indo-Pacific Oceans.The nudibranchs in this genus often show extraordinary mimicry, each species very closely resembling its prey species, which are octocorals, a kind of soft coral.They are also unusual in that they are able to utilize zooxanthellae from their prey, in a symbiotic relationship that provides them with extra nutrition from photosynthesis, hence they are one of only two groups of "solar-powered" sea slugs" (also see the Sacoglossa).