What is "onchidiidae"

Onchidiidae are a family of small, air-breathing sea (and land) slugs. They are shell-less marine (except of 5 species) pulmonate gastropod molluscs. Onchidiidae is the only family within the superfamily Onchidioidea.

These animals are quite unusual in that they are emphatically not opisthobranchs with gills, as are almost all of the sea slugs. Instead these creatures are pulmonates. They are more closely related to air-breathing land and freshwater snails and slugs than they are to most other sea snails and sea slugs.

This family has no subfamilies (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005).

There are 143 species names within the Onchidiidae, but a detailed revision has not been made yet, because there is no living malacologist expert enough on the whole group to properly identify them.