Kingdom Animalia Linnaeus, 1758 - animals
   Phylum Pogonophora Johansson, 1937 - beard worms see Family Siboglinidae Caullery, 1914
     Order Athecanephria A.V. Ivanov, 1955 see Family Siboglinidae Caullery, 1914
       Family Oligobrachiidae see Family Siboglinidae Caullery, 1914
         Genus Birsteinia Ivanov, 1952
         Genus Crassibrachia
         Genus Nereilinum Ivanov, 1961
         Genus Oligobrachia Ivanov, 1957
         Genus Unibrachium Southward, 1973