Belongs within: Hexacorallia.
The Zoanthidea are clonal, soft-bodied anthozoans with two rows of marginal tentacles (Daly et al. 2007).
<==Zoanthidea [Zoanthinaria]
| i. s.: Gerardia Lacaze Duthiers 1864O01
| Acrozoanthus australiae Saville-Kent 1893RL03
| Abyssoanthus [Abyssoanthidae]DB07
| `--A. nankaiensisDB07
|--+--Nanozoanthus harenaceusMQ21
| `--Microzoanthus occultusMQ21
`--+--MacrocneminaRL03
| |--ParazoanthidaeDFC03
| | |--Savalia savaglia Bertoloni 1819RB14, RB12
| | `--ParazoanthusRL03
| | |--P. axinellaeRB14
| | |--P. elongatusMQ21
| | |--P. puertoricenseRB14
| | `--P. swifti (Duchassaing & Michelotti 1860) [=Gemmaria swifti]RL03
| `--Epizoanthus [Epizoanthidae]MQ21
| |--E. arenaceaM62
| |--E. illoricatusRB14
| |--E. paguricolaRB14
| `--E. scotinusRB14
`--+--+--HydrozoanthusMQ21
| | |--H. gracilisRB14
| | `--H. tunicansRB14
| `--Neozoanthus [Neozoanthidae]MQ21
| `--N. uchinaMQ21
`--+--Zoanthus [Zoanthidae]MQ21
| | i. s.: Z. coppingeri Haddon & Shackleton 1891 [incl. Z. pacificus Walsh & Bowers 1971]RL03
| | Z. ellisiiG20
| | Z. giganteusMQ21
| |--Z. sociatus (Ellis 1767)MQ21, D84 [=Hydra sociataG20]
| `--+--Z. pulchellusMQ21
| `--Z. sansibaricusMQ21
`--Sphenopidae [Brachycnemina]RL03
|--Palythoa Lamouroux 1816RL03
| | i. s.: *P. mammillosa (Ellis & Solander 1786) [=Alcyonium mammillosum]RL03
| | P. caesia Dana 1846RL03
| | P. caribaeorum Duchassaing & Michelotti 1864 [=P. caribaea (l. c.)]RL03
| | P. tuberculosa (Esper 1809)RL03
| |--P. heliodiscusMQ21
| `--+--P. mutukiMQ21
| `--+--P. mizigamaMQ21
| `--Sphenopus Steenstrup 1856 non Trin. 1820 (ICBN)MQ21, RL03
| `--S. marsupialisMQ21
`--Protopalythoa Verrill 1900 [=Gemmaria Duchassaing & Michelotti 1860 non McCrady 1857]RL03
|--*P. variabilis (Duerden 1898) [=Gemmaria variabilis]RL03
|--‘Gemmaria’ aspera Carlgren 1900RL03
|--‘Mamillifera’ brevis Duchassaing 1850RL03
|--‘Gemmaria’ canariensis Haddon & Duerden 1898RL03
|--‘Mamillifera’ clavata Duchassaing 1850RL03
|--P. fusca (Duerden 1898) [=Gemmaria fusca]RL03
|--P. grandiflora (Verrill 1900) [=Palythoa grandiflora]RL03
|--P. grandis Verrill 1900RL03
|--P. heideri (Carlgren 1954) [=Palythoa heideri]RL03
|--P. heliodiscus Ryland & Lancaster 2003RL03
|--‘Gemmaria’ macmurrichi Haddon & Shackleton 1891RL03
|--‘Gemmaria’ multisulcata Carlgren 1900RL03
|--P. mutuki (Haddon & Shackleton 1891) (see below for synonymy)RL03
|--‘Palythoa’ psammophilia Walsh & Bowers 1971RL03
|--‘Gemmaria’ rusei Duchassaing & Michelotti 1860 [=G. riisei (l. c.)]RL03
|--‘Palythoa’ singaporensis Pax & Müller 1956RL03
|--P. toxica (Walsh & Bowers 1971) [=Palythoa toxica]RL03
|--‘Gemmaria’ tubulifera Carlgren 1900RL03
`--‘Zoanthus’ vestitus Verrill 1928RL03
Protopalythoa mutuki (Haddon & Shackleton 1891) [=Gemmaria mutuki; incl. G. arenacea Wilsmore 1909, Palythoa australiensis Carlgren 1950, Protopalythoa australiensis, Palythoa singaporensis Pax & Müller 1956, Gemmaria willeyi Hill & Whitelegge 1898, Palythoa yongei Carlgren 1937]RL03
*Type species of generic name indicated
References
[DB07] Daly, M., M. R. Brugler, P. Cartwright, A. G. Collins, M. N. Dawson, D. G. Fautin, S. C. France, C. S. McFadden, D. M. Opresko, E. Rodriguez, S. L. Romano & J. L. Stake. 2007. The phylum Cnidaria: a review of phylogenetic patterns and diversity 300 years after Linnaeus. Zootaxa 1668: 127–182.
[DFC03] Daly, M., D. G. Fautin & V. A. Cappola. 2003. Systematics of the Hexacorallia (Cnidaria: Anthozoa). Zoological Journal of the Linnean Society 139: 419–437.
[D84] Dardeau, M. R. 1984. Synalpheus shrimps (Crustacea: Decapoda: Alpheidae). I. The Gambarelloides group, with a description of a new species. Memoirs of the Hourglass Cruises 7 (2): 1–125.
[G20] Goldfuss, G. A. 1820. Handbuch der Naturgeschichte vol. 3. Handbuch der Zoologie pt 1. Johann Leonhard Schrag: Nürnberg.
[MQ21] McFadden, C. S., A. M. Quattrini, M. R. Brugler, P. F. Cowman, L. F. Dueñas, M. V. Kitahara, D. A. Paz-García, J. D. Reimer & E. Rodríguez. 2021. Phylogenomics, origin, and diversification of anthozoans (phylum Cnidaria). Systematic Biology 70 (4): 635–647.
[M62] Monniot, F. 1962. Recherches sur les graviers a Amphioxus de la région de Banyuls-sur-Mer. Vie et Milieu 13: 231–322.
[O01] Opresko, D. M. 2001. Revision of the Antipatharia (Cnidaria: Anthozoa). Part I. Establishment of a new family, Myriopathidae. Zoologische Mededelingen 75 (17): 343–370.
[RB12] Rodríguez, E., M. Barbeitos, M. Daly, L. C. Gusmão & V. Häussermann. 2012. Toward a natural classification: phylogeny of acontiate sea anemones (Cnidaria, Anthozoa, Actiniaria). Cladistics 28 (4): 375–392.
[RB14] Rodríguez, E., M. S. Barbeitos, M. R. Brugler, L. M. Crowley, A. Grajales, L. Gusmão, V. Häussermann, A. Reft & M. Daly. 2014. Hidden among sea anemones: the first comprehensive phylogenetic reconstruction of the order Actiniaria (Cnidaria, Anthozoa, Hexacorallia) reveals a novel group of hexacorals. PLoS One 9 (5): e96998.
[RL03] Ryland, J. S., & J. E. Lancaster. 2003. Revision of methods for separating species of Protopalythoa (Hexacorallia: Zoanthidea) in the tropical West Pacific. Invertebrate Systematics 17: 407–428.