| image = Notodoris minor.jpg | image_caption = Notodoris minor | regnum = Animalia | phylum = Mollusca | classis = Gastropoda | unranked_familia = clade Heterobranchia informal group Opisthobranchia | | subdivision_ranks = Unranked clades | subdivision = Cephalaspidea Sacoglossa Anaspidea Notaspidea Thecosomata Gymnosomata Nudibranchia }} An opisthobranch 's any member of the very large and diverse group of rather specialized, highly evolved marine slugs and snails (marine gastropod mol… (More on Opisthobranchia)