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 spectactular group - it has also been called Gymnoblastea, or, with or without an emended ending "-ae", Anthoathecata, Athecata, Hydromedusa or Stylasterina. There are about 1,200 species worldwide.
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 are solitary animals, with tentacles arising from the bell margin, lacking statocysts but possessing radial canals. Their gonads are on the manubrium ("handle").
Their close relationship to the Leptomedusae has been long known. But it was believed that these two were also close to the Limnomedusae. Actually, their closest relative are the highly advanced Siphonophorae, whereas the Limnomedusae are simply a rather primitive group that is not very closely related to these three Leptolinae but might actually belong to the Trachylinae subclass. The family Clathrozoellidae is placed with the Filifera in some treatments; in others it is placed in the Leptomedusae and sometimes even synonymized with their family Clathrozoidae. The supposed athecate family Monobrachiidae apparently belongs in the Olindiasidae of the Limnomedusae.
The Porpitidae are highly aberrant group, and were at one time considered an own order "Chondrophora". But actually they are derived from Zancleida. Halammohydridae and Otohydridae, sometimes placed here, actually appear to be trachyline hydrozoans of the order Actinulidae. Similarly, the Laingiidae, also long considered a distinct order Laingiomedusae, might belong in the Pandeida.
Basal or incertae sedis
US Patent Issued to Zakrytoe Aktsionernoe Obschestvo 'Evrogen' on May 31 for "Fluorescent Proteins and Chromoproteins from Non-Aequorea Hydrozoa Species and Methods for Using Same" (Russian Inventors)
Jun 03, 2011; ALEXANDRIA, Va., June 3 -- United States Patent no. 7,951,923, issued on May 31, was assigned to Zakrytoe Aktsionernoe Obschestvo...