living organisms see Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
   Superkingdom Eukaryotae see Domain Eukaryota Chatton, 1925
     Kingdom Animalia Linnaeus, 1758 - animals
       Subkingdom Eumetazoa Butschli, 1910 see [unranked] Eumetazoa Bütschli, 1910
         Phylum Mollusca Linnaeus, 1758 - molluscs
           Class Gastropoda Cuvier, 1795 - snails and slugs
             Subclass Opisthobranchia Milne-Edwards, 1848 - opisthobranchs see Order Opisthobranchia Milne-Edwards, 1848
               1 Order Cephalaspidea Fischer, 1883
               2 Order Runcinoidea Adams & Adams, 1854 see Suborder Cephalaspidea Fischer, 1883
               3 Order Acochlidioidea Küthe, 1935 see Order Acochlidia Odhner, 1937
               4 Order Sacoglossa Ihering, 1876 - sacoglossans
               5 Order Anaspidea Fischer, 1883 - sea hares
               6 Order Notaspidea Fischer, 1883 see Suborder Notaspidea Fischer, 1883
               7 Order Thecosomata Blainville, 1824 - shelled pteropods see Suborder Thecosomata Blainville, 1824
               8 Order Gymnosomata Blainville, 1824 - naked pteropods see Suborder Gymnosomata Blainville, 1824
               9 Order Nudibranchia Cuvier, 1814 - "true" nudibranchs