Costasiella is a genus of sacoglossan sea slugs, a shell-less marine opisthobranch gastropod mollusks in the family Costasiellidae. The most recent diagnosis of the genus Costasiella is by the Dutch malacologist Cornelis Kees Swennen (2007).
Species taxanomy provided by GBIF Secretariat (2022). GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei accessed via GBIF.org on 2023-06-13; License: CC BY 4.0