Opisthobranchia
— Navneord
– Engelsk
~ gastropods having the gills when present posterior to the heart and having no operculum: includes sea slugs; sea butterflies; sea hares
Opisthocomidae
— Navneord
– Engelsk
~ comprising the hoatzins
Opisthocomus
— Navneord
– Engelsk
~ type genus of the Opisthocomidae: hoatzins
Opisthocomus hoazin
— Navneord
– Engelsk
~ crested ill-smelling South American bird whose young have claws on the first and second digits of the wings