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Anthomedusae or Anthomedusa, the athecate hydroids, are an order of the Hydrozoa, a class of marine invertebrates belonging to the phylum Cnidaria. A profusion of alternate scientific names exists for this long-known, heavily discussed, and spectacular group. It has also been called Gymnoblastea and (with or without an emended ending ''-ae'') Anthoathecata, Athecata, Hydromedusa, and Stylasterina. There are about 1,200 species worldwide.〔Schuchert, P. (2014). Anthoathecata. Accessed through: Schuchert, P. (2014) World Hydrozoa database at http://www.marinespecies.org/hydrozoa/aphia.php?p=taxdetails&id=13551 on 2014-10-31〕 These hydrozoans always have a polyp stage. Their hydranths grow either solitary or in colonies. There is no firm perisarc around the polyp body. The medusae, or jellyfish, are solitary animals, with tentacles arising from the bell margin, lacking statocysts but possessing radial canals. Their gonads are on the manubrium ("handle").〔Bouillon, J.; Gravili, C.; Pagès, F.; Gili, J.-M.; Boero, F. (2006). An introduction to Hydrozoa. Mémoires du Muséum national d'Histoire naturelle, 194. Muséum national d'Histoire naturelle: Paris, France. ISBN 2-85653-580-1. 591pp. + 1 cd-rom〕 Except in Eudendriidae and Laingiidae, the cnidome has desmonemes.〔 ==Systematics〔(Schuchert (2014), World Hydrozoa database. )〕== Their close relationship to the Leptomedusae has been long known, but it was formerly believed that these two were also close to the Limnomedusae. Actually, their closest relatives are the highly advanced Siphonophorae, whereas the Limnomedusae are simply a rather primitive group, not very closely related to these three Leptolinae, but might actually belong to the Trachylinae subclass. Some uncertainty existed regarding the internal taxonomy. The most simple scheme, adopted until recently by most authors since it was proposed in 1913, divided the order into a smaller suborder (Filifera) and a larger one (Capitata), but several unusual Anthomedusae refused to fit into this arrangement, and a considerable number only did so awkwardly. The Porpitidae, for example, are highly aberrant group, and were at one time even considered a separate order "Chondrophora". But actually, they are derived from Zancleida. However, in the early 21st century, the well-known ''Hydra'' and its relatives – in fact most of the supposed filiferan infraorders Tubulariida and Moerisiida – were determined to be, in fact, a very ancient lineage, subsequently recognized as suborder Aplanulata. Now, though not all Anthomedusae have been firmly placed in the phylogeny, most are fairly certainly assigned at least to one of the major subdivisions. As a notable exception, a prehistoric family, the Heterastridiidae, is still highly disputed regarding its relationships to the extant taxa, as are a small number of very aberrant and/or little-known species such as the aptly named ''Saccohydra problematica''. The family Clathrozoellidae is placed with the Filifera here; in others it is placed in the Leptomedusae and sometimes even synonymized with their family Clathrozoidae. By contrast, the supposed filiferan genus ''Anthohydra'' is in fact the leptomedusan ''Eugymnanthea''; similarly, "''Gammaria''" is also a leptomedusan and properly spelled ''Grammaria''. The supposed athecate family Monobrachiidae is apparently a close relative of the Olindiasidae, and belongs in the Limnomedusae. Halammohydridae and Otohydridae, sometimes placed here, actually appear to be trachyline hydrozoans of the order Actinulidae. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Anthomedusae」の詳細全文を読む スポンサード リンク
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