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TAXONOMY OF THE DEUTEROSTOMATA

INTRODUCTION TO THE DEUTEROSTOMES

The deuterostomes are united as bilaterians in their form of developmental history.  Specifically, the fate of the deuterostome blastopore is that it becomes the anus.  Also, the deuterostomes tend to develop by radial cleavage and form an endocoelic coelom.  In some ways, particularly the locations of the nerve cords relative to the food tube, the deuterostome architecture is like that of an inverted or upside-down worm.  Some systems, particularly those based on morphological characters, place the lophophorates in the deuterostomes.  I have sided with the molecular phylogeneticists in this regard.  In all systems, the position of the chaetognaths is problematic, so I have left them in the deuterostomes until there is some consensus as to their position.  The system that I present here follows Nielsen (2001) in raising the traditional subphyla of the "Chordata" to the phylum level.  Also, I have kept the Enteropneusta and Pterobranchia together in the phylum Hemichordata.  Like many of the protostomes, the following six phyla have a true coelom at least at some point in their developmental history.  Please consult The Major Clades of the Animal Kingdom and Cladograms of the Deuterostome Phyla for some views on the relationships of the deuterostome phyla with each other and with the other phyla of animals.

PHYLUM HEMICHORDATA

CLASS ENTEROPNEUSTA (1 ORDER)

Balanoglossus, Protoglossus, Saccoglossus, Saxipendium, Spengella, Xenopleura.

CLASS PTEROBRANCHIA (2 ORDERS)

Atubaria, Cephalodiscus, Rhabdopleura, 

CLASS PLANKTOSPHAERIDA (1 ORDER)

Planktosphaera.

PHYLUM ECHINODERMATA

  SUBPHYLUM PELMATOZOA 

CLASS CRINOIDEA (5 ORDERS)

Antedon, Asterometra, Cenocrinus, Comantheria, Comanthina, Isometra, Metacrinus, Neometra, Phixometra, Zygometra.

  SUBPHYLUM ELEUTHEROZOA

CLASS ASTEROIDEA (7 ORDERS)

Platysterias.

Astropecten, Caymanostella, Ctenodiscus, Lethmaster.

Amphiaster, Archaster, Asterodon, Chaetaster, Hoplaster, Linckia, Odonaster, Oreaster.

Acanthaster, Echinaster, Henricia, Pteraster, Remaster, Solaster. 

Asterias, Brisinga, Evasterias, Heliaster, Leptasterias, Pisaster, Pycnopodia, Styasterias.

Luidia, Dermasterias, Patiria, Echinaster, Pteraster, Asterina.

CLASS CONCENTRICYLOIDEA (1 ORDER?)

Xyloplax.

CLASS OPHIUROIDEA (3 ORDERS)

Ophiocanops.

Asteronyx, Astrodia, Gorgonocephalus, Ophiomyxa.

Amphiophiura, Ophiactis, Ophiocoma, Ophioderma, Ophiolepis, Ophiomusium, Ophionereis, Ophiopholis, Ophiothrix, Ophiura.

CLASS ECHINOIDEA (15 ORDERS DISTRIBUTED IN 2 SUBCLASSES)

SUBCLASS CIDAROIDEA

Cidaris, Eucidaris,  Notocidaris, Phyllacanthus, Psychocidaris.

SUBCLASS EUECHINOIDEA

Araeosoma, Asthenosoma, Phormosoma, Sperosoma.

Astropyga, Aspidodiadema, Caenopedina, Diadema, Micropyga, Plesiodiadema.

Arbacia, Echinometra, Echinus, Heterocentrotus, Lytechinus, Paracentrotus,  Salenia, Strongylocentrotus, Toxopneustes, Tripneustes.

Cassidulus, Clypeaster, Dendraster, Echinocardium,  Echinodiscus, Echinolampus, Encope, Fibularia, Hemiaster, Lovenia, Maretia,  Mellita, Meoma, Metalia, Micropetalon, Spatanga, Urechinus.

Apatopygus, Claveriosoma, Diadema, Echinarachinus, Echinoneus, Moira.

CLASS HOLOTHUROIDEA (6 ORDERS DISTRIBUTED IN 3 SUBCLASSES)

SUBCLASS DENDROCHIROTACEA

Echinocucumis, Holothuria, Mitsukuriella, Rhopalodina, Sphaerothuria, Vaneyella, Ypsilothuria.

Cucumaria, Eupentacta, Paracucumis, Peniagone, Placothuria, Psolus, Thyone, Thyonepsolus.

SUBCLASS ASPIDOCHIROTACEA

Actinopyga, Astichopus, Bathyplotes, Holothuria, Isostichopus, Parastichopus, Stichopus.

Benthodytes, Deima, Enypniastes, Pelagothuria, Scotoplanes.

SUBCLASS APODACEA

Caudina, Molpadia, Trochoderma.

Euapta, Leptosynapta, Synapta. 

PHYLUM UROCHORDATA

CLASS ASCIDIACEA (4 ORDERS)

Ascidia, Botryllus, Chelyosoma, Ciona, Clavelina, Corella, Diazona, Diplosoma,  Halocynthia, Lissoclinum, Molgula, Polycarpa, Psammascidia, Pyura, Styela.

CLASS THALIACEA (3 ORDERS)

Dolioletta, Doliolum, Pyrosoma, Salpa, Thetys.

CLASS APPENDICULARIA (ALSO CALLED LARVACEA, 1 ORDER)

Fritillaria, Oikopleura, Stegasoma.

CLASS SORBERACEA (1 ORDER)

Octacnemus.

PHYLUM CEPHALOCHORDATA (ALSO CALLED ACRANIA)

CLASS BRANCHIOSTOMATA (1 ORDER)

Asymmetron, Branchiostoma (Amphioxus), Epigonichthyes.

PHYLUM CRANIATA 

SUBPHYLUM MYXINOMORPHI

CLASS MYLLOKUNMINGIIDA+

CLASS MYXINI (HAGFISHES)

SUBPHYLUM VERTEBRATA

SUPERCLASS PETROMYZONTOMORPHI 

CLASS PETROMYZONTIDA (LAMPREYS)

SUPERCLASS CONODONOMORPHI+

CLASS CONODONTA+

SUPERCLASS PTERASPIDOMORPHI+

CLASS PTERAPSIDA+ 

SUPERCLASS ANASPIDOMORPHI+

CLASS ANASPIDA

SUPERCLASS THELODONTOMORPHI+

CLASS THELODONTI

SUPERCLASS OSTEOSTRACOMORPHI

CLASS CEPHALASPIDOMORPHI

SUPERCLASS GNATHOSTOMATA

CLASS PLACODERMI+

CLASS CHONDRICHTHYES (SHARKS, SKATES, RAYS, CHIMERAS)

CLASS ACANTHODII+

CLASS OSTEICHTHYES (THE BONY FISHES)

CLASS STEGOCEPHALI+ -(THE TRANSITIONAL EARLY TETRAPODS)

CLASS BATRACHOMORPHA (CONTAINS EXTANT AMPHIBIA)

CLASS PROAMNIOTA+ (LEPOSPONDYLI-REPTILIOMORPHA CLADE)

CLASS EOSYNAPSIDA+- THE MAMMAL-LIKE REPTILES

CLASS MAMMALIA (CONTAINS EXTANT MAMMALS)

CLASS ANAPSIDA (CONTAINS TURTLES)

CLASS EODIAPSIDA+ (CONTAINS STEM DIAPSIDS AND ICHTHYOSAURS)

CLASS LEPIDOSAUROMORPHA (CONTAINS EXTANT LIZARDS, SNAKES, AND TUATARAS)

CLASS ARCHOSAUROMORPHA (CONTAINS CROCODILIANS & BIRDS)

By Jack R. Holt.  Last revised: 02/01/2009