Thecreme or orange coloured body is slender with long paired pinkish cerata. The cerata have a bluish-white stripe running down their length. There is an opaque white median dorsal. The rhinophores are smooth. This species contains no zooxanthellae.Cerata with a bluish-white stripe running down their length, as does the body. Rhinophores are smooth.
This coral nudibranch contains no zooxanthellae.
Phyllodesmium horridum feeds on sea fans (gorgonians) of the genus Melitodes and genus Acabaria.
Similar to Phyllodesmium serratum which is known from Australia and Japan.