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 Echinodermata Bruguière, 1789 - echinoderms
           Subphylum Echinozoa von Zittel, 1895 see Infraphylum Echinozoa Haeckel, in Von Zittell, 1895
             Class Echinoidea (Leske, 1778) - sea urchins and sand dollars
               Subclass Euechinoidea Bronn, 1860
                 Superorder Gnathostomata Zittel, 1879
                   Order Clypeasteroida A. Agassiz, 1872 - true sand dollars
                     Suborder Clypeasterina von Zittel, 1879
                       Family Arachnoididae
                         1 Genus Arachnoides Leske, 1778
                         2 Genus Fellaster Durham, 1954
                         3 Genus Ammotrophus Clark, 1928