The endless forms are the most differentiated—how taxonomic pseudo-optimization masked natural diversity and evolution: the nudibranch case

Abstract In this study, a global-encompassing, fine-scale differentiated taxonomy is consistently presented from the high level of a major nudibranch suborder, Aeolidacea, and then consequentially to lower levels of superfamilies, families, genera, and species to conjoin the underlying evolutionary pathways of aeolidacean nudibranchs and systematic representation to a maximal degree. The suborder Aeolidacea is reinstated and the superfamily system of Aeolidacea is reformed; 10 aeolidacean superfamilies are recognized encompassing 29 families in an all-family Synopsis, and the superfamily Embletonioidea is included in addition. Two new families, Chudidae fam. nov. and Hantazuidae fam. nov., are described, which show unique morphological and molecular patterns. Seven new species are described within various superfamilies, and five species are reinstated. The genus-level taxonomy of the family Coryphellidae is revisited, 11 genera are recognized, including nine reinstated and two new genera. We show that recent synonymization of all valid Coryphellidae genera into just a single genus was based on an erroneous phylogenetic analysis, the careless treatment of morphological characters, and established preconceptions. Uniting fine-scale morphological and molecular data, order-level nudibranch taxonomy is refined, order Nudibranchia is restricted, and order Doridida is reinstated. Within the order Nudibranchia, five suborders are recognized: Arminacea, restricted, reinstated; Tritoniacea, reinstated; Dendronotacea, restricted, reinstated; Janolacea, reinstated; and Aeolidacea, revised, reinstated.