INTRODUCTION TO THE RADIATA

These organisms have radial symmetry and tissues that arise from two cell layers (diploblastic).  The tissues are arranged into organs.  Almost all are marine.  Some radiates go through an alternation of a sessile vegetative stage (the hydroid) and a motile sexual stage (the medusoid).  Many produce free-swimming larval forms.  Because the Radiates resemble large free-living gastrulas, the shared trait of diploblasty likely is primitive.  Thus, they are grouped together on the basis of a shared primitive trait and therefore paraphyletic.  Please consult The Major Clades of the Animal Kingdom for some views on the relationships of the radiate phyla with each other and with the other phyla of the animal kingdom.

I have included the Myxozoa within the Radiata because it is most certainly a highly reduced Cnidarian.  Traditionally, it has been considered a "protozoan" and before the demise of the taxon, Protozoa, was a member of the Sporozoa.  Their particular relationship with other animal groups is still under dispute.  However, what I interpret as clear affinities with the Cnidaria have prompted me to include the Myxozoa as a separate phylum in the Radiata.

PHYLUM CNIDARIA

CLASS HYDROZOA (5 ORDERS)

Bouganvilla, Calycopsis, Eleutheria, Eudendrium, Hydra, Hydractina, Hydrocoryne, Janaria, Lar, Pennaria, Polyorchis, Sarsia, Staurocladia, Stylactis,Tubularia, Abietinaria, Aequoria, Aglaophenia, Bonneviella, Campanularia, Cuvieria, Obelia, Gonionemus, Gonothyrea, Lovenella, Plumularia, Sertularia, Aegina, Botrynema, Craspedacusta, Cunina, Hydroctena, Liriope, Polypodium, Rhopalonema, Solmissus, Agalma, Apolemia, Eudoxoides, Nectocarmen, Physalia, Rhyzophysa, Sphaeronectes, Porpita, Velella, Halammohydra, Otohydra.

CLASS SCYPHOZOA (4 ORDERS)

Aurelia, Cyanea, Haliclystus, Lucernaria, Atolla, Linuche, Naustihoe, Periphylla, Stephanoscyphus, Tetraplatia, Chrysaora, Pelagia, Sanderia, Stygiomedusa, Cassiopeia, Cephea, Eupilema, Mastigias, Rhizostoma, Stomolophus.

CLASS CUBOZOA (1 ORDER)

Tripedalia, Carybdea, Chironex, Tamoya.

CLASS ANTHOZOA

SUBCLASS CERIANIPATHARIA (2 ORDERS)

Cerianthus, Antipathes, Arachnanthus, Botruanthus, Ceriantheomorphe, Ceriantheopsis, Pachycerianthus.

SUBCLASS OCTOCORALLIA (=ALCYONARIA; 8 ORDERS)

Alcyonium, Anthomastus, Ceratocaulon, Gersemia, Parerythropodium, Pseudogorgia, Acanthogorgia, Biareum, Corallium, Eugorgia, Eunicella, Isis, Leptogorgia, Muricea, Parisis, Psamogorgia, Swiftia, Epiphaxum, Heliopora, Anthoptilum, Balticina, Cavernularia, Funicularia, Ptilosarcus, Stylatula, Umbellula, Virgularia, Haimea, Hartea, Monoxenia, Psuchastes, Taiaroa, Clavularia, Cornularia, Sarcodictyon, Tubipora, Gorgonia, Renilla, Pennatula, Coelogorgia, Paratelesto, Telesto, Telestula.

SUBCLASS HEXACORALLIA (=ZOANTHARIA; 4 ORDERS)

Adamsia, Aiptasia, Alicia, Anthopleura, Anthothoe, Bartholomea, Bunodactis, Calliactus, Condylanthus, Diadumene, Edwardsia, Epiactus, Halcampa, Haliplanella, Heteractis (Radianthus), Liponema, Metridium, Peachia, Phyllodiscus, Ptychodactis, Stichodactyla, Stomphia, Triactis, Agaricia, Astrangia, Balanophyllia, Dendrogyra, Flabellum, Actinia, Fungia, Goniopora, Letepsammia, Meandrina, Montipora, Oculina, Pachyseris, Porites, Psammocora, Siderastraea, Stylophora, Epizoanthus, Isaurus, Isozoanthus, Palythoa, Parazoanthus, Thoracactus, Zoanthus, Amplexidiscus, Corynactis, Rhodactis, Ricordea.

PHYLUM MYXOZOA

CLASS MYXOSPOREA (2 ORDERS)

CLASS ACTINOSPOREA (1 ORDER)

Triactinomyxon, Tetractinomyxon, Sphaeractinomyxon.

PHYLUM CTENOPHORA

CLASS TENTACULATA (6 ORDERS)

Cestum, Velamen, Aulococtena, Bathyctena, Callianira, Dryodora, Euplokamis, Hormiphora, Lampea, Mertensia, Pleurobrachia, Tinerfe, Ganesha, Bolinopsis, Deiopea, Leucothea, Mnemiopsis, Ocyropsis, Coeloplana, Ctenoplana, Lyrocteis, Savangia, Tjalfiella.

CLASS NUDA (1 ORDER)

Beroe, Neis.