
Belongs within: Radiozoa.
The Arthracanthida are a group of acanthareans that have the ecto- and endoplasm separated by a thick capsule (Adl et al. 2012).
Characters (from Adl et al. 2012): Thick capsule clearly demarcates pigmented endoplasm from ectoplasm; axopodia with hexagonal microtubular arrays; many nuclei in endoplasm; algal symbionts in all known species, except at reproduction; sexual reproduction without gamontocyst.
<==ArthracanthidaAS12 | i. s.: DictyacanthaAS12 | PhractopeltaAS12 | PhyllostaurusAS12 | PleuraspisAS12 |--AcanthometraH04 | |--Stauracantha quadrifurcaAS12, H04 | |--Lithoptera dodecapteraH04 | |--Pristacantha Haeckel 1887H04, AA05 | | `--P. polyodonH04 | |--Acantholonche Haeckel 1881H04, AA05 | | |--A. favosaH04 | | `--A. peripolarisH04 | `--Xiphacantha Haeckel 1862H04, AA05 | |--X. alataBM05 | |--X. ciliataH04 | `--X. spinulosaH04 `--AcanthophractaH04 | i. s.: Diporaspis nephrophoraH04 | Echinaspis echinoidesH04 | Diplocolpus costatatusH04 | Diploconus hexaphyllusAS12, H04 | Icosaspis elegansH04 | Hexaconus serratusH04 | Hexacolpus nivalisH04 | LychnaspisH04 | |--L. mirandaH04 | `--L. polyancistraH04 `--Dorataspidae [Dorataspacea, Dorataspida, Dorataspididae]LT61 |--Dorataspis typicaH04 `--Orophaspis Haeckel 1881 [=Stegaspis Haeckel 1881 non Germar 1833]LT61 `--*O. diporaspis Haeckel 1887 [=*Stegaspis diporaspis]LT61
*Type species of generic name indicated
References
[AS12] Adl, S. M., A. G. B. Simpson, C. E. Lane, J. Lukeš, D. Bass, S. S. Bowser, M. W. Brown, F. Burki, M. Dunthorn, V. Hampl, A. Heiss, M. Hoppenrath, E. Lara, E. Le Gall, D. H. Lynn, H. McManus, E. A. D. Mitchell, S. E. Mozley-Stanridge, L. W. Parfrey, J. Pawlowski, S. Rueckert, L. Shadwick, C. L. Schoch, A. Smirnov & F. W. Spiegel. 2012. The revised classification of eukaryotes. Journal of Eukaryotic Microbiology 59 (5): 429–493.
[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.
[BM05] Bass, D., D. Moreira, P. López-García, S. Polet, E. E. Chao, S. von der Heyden, J. Pawlowski & T. Cavalier-Smith. 2005. Polyubiquitin insertions and the phylogeny of Cercozoa and Rhizaria. Protist 156: 149–161.
[H04] Haeckel, E. 1899–1904. Kunstformen der Natur. Bibliographisches Institut: Leipzig und Wien.
[LT61] Loeblich, A. R., Jr & H. Tappan. 1961. Remarks on the systematics of the Sarkodina (Protozoa), renamed homonyms and new and validated genera. Proceedings of the Biological Society of Washington 74: 213–234.