See text Costasiellidae is a taxonomic family of small to minute sacoglossan sea slugs.
These are marine opisthobranch gastropod mollusks belonging to the superfamily Plakobranchoidea.
[1] These sea slugs resembling nudibranchs, but are not closely related to them.
This family has no subfamilies.
The following genera belong to the family Costasiellidae: