Zygocircus productus, from here.

Belongs within: Radiozoa.
Contains: Popofskyelloidea, Cessipyloroidea, Pylentonemoidea, Archipilioidea, Acropyramidoidea, Lychnocanioidea, Eucyrtidioidea, Stichocapsoidea, Amphipyndacioidea, Cannobotryoidea, Triospyrididae, Acanthodesmiidae.

The Nassellaria are a major group of radiolarians known from the Cambrian to the present. Members possess a heteropolar or bilaterally symmetrical skeleton comprising an inner frame and an external shell. Palaeozoic members of the Nassellaria are assigned to the order Pylomariata which persists to the early Cretaceous and is characterised by the presence of a pylome, a basal opening in the oral region of the test (Afanasieva et al. 2005).

Characters (from Afanasieva et al. 2005): Heteropolar or bilaterally symmetrical. Skeleton based on inner frame in shape of hollow sphere, polyhedron or spicule, and external shell (conical, pyramidal, spindle-shaped, bell-shaped, helmet-shaped, cap-shaped, or differently shaped test or external skeleton), often segmented. External skeleton subdivided into four main portions: cephalis, thorax, abdomen, and postabdomen. Postabdomen may be further segmented (2–15 or more segments). Inner skeletal polyhedron (5–30 μm in diameter) and spicule included in cephalis, median bar of spicule separating cephalis from thorax. Number and position of rays (spines) of spicule stable: spines A, D, and 2l arising from one end of median bar (MB), spines V, 2L, and Ax extending from another end.

<==Nassellaria [Nassellarida]
    |    |--PopofskyelloideaAA05
    |    |--+--CessipyloroideaAA05
    |    |  `--PylentonemoideaAA05
    |    `--Proventocitidae [Proventocitoidea]AA05
    |         |--Procyrtis Li 1995AA05
    |         |--Ulcundia Nazarov 1974AA05
    |         |    `--U. incompertaAA05
    |         `--Proventocitum Nazarov & Ormiston 1990AA05
    |              `--P. procerulum (Nazarov in Nazarov & Popov 1980)MB07
    |--Cyrtidinata [Cyrtoidea]AA05
    |    |  i. s.: Anthocyrtium Haeckel 1887H04, AA05
    |    |           `--A. campanulaH04
    |    |         Alacorys Haeckel 1881H04, AA05
    |    |           `--A. bismarckiiH04
    |    |--ArchipilioideaAA05
    |    |--AcropyramidoideaAA05
    |    |--LychnocanioideaAA05
    |    |--EucyrtidioideaAA05
    |    |--StichocapsoideaAA05
    |    |--AmphipyndacioideaAA05
    |    `--CannobotryoideaAA05
    `--Spyridinata [Spyrida, Spyroidea, Stephaniicae, Stephoidea]AA05
         |  i. s.: Clathrospyris Haeckel 1881H04, AA05
         |           `--C. pyramidalisH04
         |         Pylospyris Haeckel 1881H04, AA05
         |           `--P. canariensisH04
         |         Sepalospyris Haeckel 1881H04, AA05
         |           `--S. pagodaH04
         |         Dictyospyris Ehrenberg 1847H04, AA05
         |           |--D. anthophoraH04
         |           `--D. stalactitesH04
         |         Elaphospyris Haeckel 1881H04, AA05
         |           `--E. cervicornisH04
              |--Cortina Haeckel 1881AA05
              |--Plagiocarpa Haeckel 1881AA05
              |--Stephanium Haeckel 1887AA05
              |    `--S. quadrupesAA05
              `--Zygocircus Buetschli 1882AA05
                   `--Z. productusAA05
Nassellaria incertae sedis:
  Fuelopicyrtis Kozur & Mostler 1981DZ03
  Recoaroella Dumitrica 1982DZ03
  Corocalyptra Haeckel 1887BC98, AA05
    `--C. craspedota (Jørgensen 1900)BC98
  Peridium Haeckel 1881BC98, AA05
    `--P. longispinum Jørgensen 1900BC98
  Acanthocorys Haeckel 1882BC98, AA05
    `--A. umbellifera (Haeckel 1862)BC98
    |--Dorypyle Squinabol 1904AA05
    |    `--D. communis (Squinabol 1903)BW04
    `--Hiscocapsa O’Dogherty 1994BW04
         `--H. asseni (Tan 1927)BW04
    |--Tertonium Dumitrica & Zügel 2003DZ03
    |    |--*T. rectum Dumitrica & Zügel 2003DZ03
    |    `--T. curvicornum Dumitrica & Zügel 2003DZ03
    `--Toritenum Dumitrica & Zügel 2003DZ03
         |--*T. hirsutum Dumitrica & Zügel 2003DZ03
         |--T. corpulentum Dumitrica & Zügel 2003DZ03
         `--‘Parvicingula’ obesa Takemura 1986DZ03
  Artostrobus Haeckel 1881BC98, AA05
    |--A. annulatus (Bailey 1856)BC98
    `--A. joergenseni Petrushevskaya 1971BC98

*Type species of generic name indicated


[AA05] Afanasieva, M. S., E. O. Amon, Y. V. Agarkov & D. S. Boltovskoy. 2005. Radiolarians in the geological record. Paleontological Journal 39 (Suppl. 3): S135–S392.

[BW04] Babazadeh, S. A., & P. de Wever. 2004. Early Cretaceous radiolarian assemblages from radiolarites in the Sistan Suture (eastern Iran). Geodiversitas 26 (2): 185–206.

[BC98] Bjørklund, K. R., G. Cortese, N. Swanberg & H. J. Schrader. 1998. Radiolarian faunal provinces in surface sediments of the Greenland, Iceland and Norwegian (GIN) Seas. Marine Micropalaeontology 35: 105–140.

[DZ03] Dumitrica, P., & P. Zügel. 2003. Lower Tithonian mono- and dicyrtid Nassellaria (Radiolaria) from the Solnhofen area (southern Germany). Geodiversitas 25 (1): 5–72.

[H04] Haeckel, E. 1899–1904. Kunstformen der Natur. Bibliographisches Institut: Leipzig und Wien.

[MB07] Maletz, J., & D. L. Bruton. 2007. Lower Ordovician (Chewtonian to Castlemainian) radiolarians of Spitsbergen. Journal of Systematic Palaeontology 5 (3): 245–288.

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