[Phylum] [Arthropoda] Siebold, 1848 - arthropods Chelicerata Heymons, 1901 Euchelicerata Weygoldt & Paulus, 1979 Pantetrapulmonata Shultz, 2007 [Order] †Haptopoda Pocock, 1911 [monotypic] Family †Plesiosironidae Pocock, 1911 [monotypic] Genus †Plesiosiro Pocock, 1911