Nudibranchia

order of molluscs Nudibranchia (Nudibranchia) is an order comprising closely related families of organisms. It contains 17 families with 31 known species. Key family groups include Aeolidiidae, Cadlinidae, Calycidorididae, Chromodorididae, Cumanotidae, and Dendronotidae. Among its members, 3 species are currently classified as threatened (Critically Endangered, Endangered, or Vulnerable). It belongs to Gastropoda (Gastropoda).