After

<==o Phascolionidae Cutler & Gibbs, 1985 [Phascoliidae Cutler & Gibbs, 1985]
   |--o Phascolion Thiel, 1875
   |  |--o (Isomya) Cutler & Cutler, 1985
   |  |  |-- P. (I.) convestitum (Sluiter, 1902) [Phascolion convestitus Sluiter, 1902; Phascolion mediterraneum Fischer, 1922; Phascolion beklemischevi Murina, 1964]
   |  |  |-- P. (I.) gerardi Rice, 1993
   |  |  |-- P. (I.) hedraeum Selenka & de Man, 1883 [Phascolion dentalicola Satí, 1937; Phascolion kurchatovi Murina, 1947]
   |  |  |-- P. (I.) lucifugax Selenka & de Man, 1883
   |  |  |-- P. (I.) microsperhoidis (Cutler & Duffy, 1972) [Phascolion microsheroidi Cutler & Duffy, 1972]
   |  |  `-- P. (I.) tuberculosum Thiel, 1875 [Tylosoma lytkenii Koren & Daneilssen, 1875; Phascolion pallidum Koren & Danielssen, 1875; Phascolion hirondellei Sluiter, 1900; Phascolion temporariae Edmonds, 1976]
   |  |--o (Lesenka) Gibbs, 1985
   |  |  |-- P. (L.) collare Selenka & de Man, 1883
   |  |  |-- P. (L.) cryptum (Hendrix, 1975) [Phascolion cryptus Hendrix, 1975]
   |  |  |-- P. (L.) hupferi Fischer, 1895 [Phascolion indicus Murina, 1974]
   |  |  |-- P. (L.) rectum Ikeda, 1904
   |  |  `--o P. (L.) valdiviae Fischer, 1916
   |  |     |-- P. (L.) v. valdiviae Fischer, 1916
   |  |     `-- P. (L.) v. sumatrense Fischer, 1916 [Phascolion murrayi Stephen, 1941]
   |  |--o (Montuga) Gibss, 1985
   |  |  `--o P. (M.) lutense Selenka, 1885
   |  |     |-- P. (M.) l. lutense Selenka, 1885 [Phascolion canum Cutler & Cutler, 1980]
   |  |     `-- P. (M.) l. pacificum Murina, 1957
   |  |--o (Phascolion) Thiel, 1875
   |  |  |-- P. (P.) abnorme Fischer, 1895 [Phascolion heteropapillosum Wesenberg-Lund, 1963]
   |  |  |-- P. (P.) bogorovi Murina, 1973
   |  |  |-- P. (P.) caupo Hendrix, 1975
   |  |  |-- P. (P.) hibridum Murina, 1981
   |  |  |-- P. (P.) medusae Cutler & Cutler, 1980
   |  |  |-- P. (P.) megaethi Cutler & Cutler, 1979
   |  |  |-- P. (P.) pharetratum Sluiter, 1902
   |  |  |-- P. (P.) psammophilus Rice, 1993
   |  |  |-- P. (P.) robertsoni Stephen & Robertson, 1952
   |  |  |--o P. (P.) strombus (Montagu, 1804) [Sipunculus strombus Montagu, 1804]
   |  |  |  |-- P. (P.) s. strombus (Montagu, 1804) [Sipunculus strombus Montagu, 1804; Sipunculus dentalii Gray, 1828; Sipunculus bernnhardus Forbes, 1841; Sipunculus capitatus Rathke, 1843; Sipunculus caementarius de Quatrefages, 1865; Phascolosoma hamulatum Packard, 1867; Phascolion spetsbergense Thiel, 1875; Phascolosoma tubicola Verrill, 1873; Sipunculus concharum Oersted, 1844; Phascolion alberti Sluiter, 1900; Phascolion artificiosus Ikeda, 1904; Phascolion mogadrense Sluiter, 1912; Phascolosoma intermedium Southern, 1913; Phascolion africanum Fischer, 1923; Phascolion brotzkajae Murina, 1964; Phascolion tortum Edmonds, 1976; Phascolion anomalus Murina, 1981]
   |  |  |  `-- P. (P.) s. cronullae Edmonds, 1980
   |  |  `-- P. (P.) ushakovi Murina, 1975
   |  `--o (Villiophora) Cutler & Cutler, 1985
   |     `-- P. (V.) cirratum (Murina, 1968) [Phascolion cirratus Murina, 1968]
   `--o Onchnesoma Koren & Danielssen, 1875
      |-- O. intermedium Murina, 1976
      |-- O. magnibathum Cutler, 1969
      |--o O. squamatum (Koren & Danielsen, 1875) [Phascolosoma squamatum Koren & Danielssen, 1875]
      |  |-- O. s. squamatum Murina, 1976 (Koren & Danielsen, 1875) [Phascolosoma squamatum Koren & Danielssen, 1875]
      |  `-- O. s. oligopapillosum Cutler, 1984
      `--o O. steenstrupii Koren & Danielssen, 1875 
         |-- O. s. steenstrupii Koren & Danielssen, 1875 [Phascolion dogieli Murina, 1964]
         `-- O. s. nudum Cutler & Cutler, 1985

Reference(s):

Special thanks to:

Jos H. M. Dols, for gathering additional information and species of these animals.