Fiona Pinnata

Fiona pinnata, common name Fiona, is a species of small pelagic sea slug, specifically a nudibranch, a marine gastropod mollusk in the superfamily Fionoidea. This nudibranch species lives worldwide on floating objects on seas, and feeds mainly on barnacles, specifically goose barnacles in the genus Lepas.

The anatomy of this species is very unusual; it does not appear to have any living close relatives. It is the only member of the genus Fiona (the genus is thus monotypic), and the genus Fiona is in turn the only genus in the family Fionidae (a monotypic family). Features that are unique to the family Fionidae, including Fiona pinnata, include:

• the oral tentacles and rhinophores look the same
• the cerata have a membrane, and have no cnidosac
• the opening of the anus is directed dorsally
• there are two genital openings of the reproductive system
• there are two jaws with a cutting-edge
• the radula looks like a column of single teeth: in each row there is only one central denticle. That one denticle has a central cusp and a few surrounding cusps.