Costasiella

Costasiella is a genus of sacoglossan sea slugs, a shell-less marine opisthobranchid gastropod mollusk in the family Costasiellidae.

The most recent diagnosis of the genus Costasiella is by the Dutch malacologist Cornelis Kees Swennen (2007).

Species
There are 17 species in the genus Costasiella
 * Costasiella arenaria K. R. Jensen, Krug, Dupont & Nishina, 2014
 * Costasiella coronata Swennen, 2007
 * Costasiella formicaria (Baba, 1959)
 * Costasiella fridae Fernández-Simón & Moles, 2023
 * Costasiella illa (Marcus, 1965)
 * Costasiella iridophora Ichikawa, 1993
 * Costasiella kuroshimae Ichikawa, 1993
 * Costasiella mandorahae Jensen 1997
 * Costasiella nonatoi Marcus & Marcus, 1960
 * Costasiella ocellifera (Simroth, 1895)
 * Costasiella pallida Jensen, 1985
 * Costasiella patricki Espinoza, DuPont & Valdés, 2014
 * Costasiella paweli Ichikawa, 1993
 * Costasiella rubrolineata Ichikawa, 1993
 * Costasiella usagi Ichikawa, 1993
 * Costasiella vegae Ichikawa, 1993
 * Costasiella virescens Pruvot-Fol, 1951
 * Species brought into synonymy:
 * Costasiella lilianae (Marcus & Marcus, 1969) - Clark (1984) : synonym of Costasiella ocellifera (Simroth, 1895)