Kingdom Animalia Linnaeus, 1758 - animals Phylum Arthropoda Siebold, 1848 - arthropods Subphylum Chelicerata Heymons, 1901 Class Pycnogonida Latreille, 1810 - pycnogonids Order †Palaeoisopoda Hedgpeth, 1978 [monotypic] 1 Family †Palaeoisopodidae Dubinin, 1957