Types of Marine Invertebrates in Britain, this includes groups that are pelagic (free living in the ocean) and may only occasionally occur in UK waters, and species that are parasitic on other marine animals.
Protozoa
Porifera
Hexactinellida (glass sponges
Calcarea (calcareous sponges)
Demospongiae (common sponges)
Placozoa
Mesozoa
Rhombozoa (rhombozoans)
Orthonecta (orthonectidans)
Cnidaria
Hydrozoa (polyps, hydras)
Scyphozoa (jellyfish)
Anthozoa (corals and anemones)
Ctenophora (sea-gooseberries)
Platyhelminthes (flatworms)
Turbellaria (free-living flatworms)
Monogenea (flukes)
Trematoda (flukes)
Cestoda (tapeworms)
Nemertea/Nemertini (ribbon and bootlace worms)
Gnathostomulida (gnathostomulans)
Gastrotricha (gastrotrichans)
Nematoda (round-worms)
Cephalorhyncha
Kinorhyncha (kinorhynchan worms)
Loricifera (loriciferans)
Priapulida (priapulid worms)
Nematomorpha (horsehair worms)
Rotifera (wheel animalcules)
Monogononta
Seisonidea
Bdelloidea
Acanthocephala (spiny-headed worms)
Cycliophora
Sipuncula (sipunculid worms)
Entoprocta (entoprocts)
Annelida (segmented worms)
Polychaeta (polychaete worms)
Clitellata
•Oligochaeta (earthworms and oligochaete worms)
Hirudinea (leeches)
Echiura (spoon worms)
Mollusca
Caudofoveata (caudofoveates)
Solenogastres (solenogasts)
Monoplacophora (monoplacophorans)
Polyplacophora (chitons)
Gastropoda (snails and slugs)
Bivalvia (bivalves)
Scaphopoda (tusk-shells)
Cephalopoda (squids and octopuses)
Arthropoda
Crustacea
•Branchiopoda (water fleas)
•Branchiura (fish lice)
•Copepoda (copepods)
•Cirripedia (barnacles)
•Ostracoda (ostracods)
•Malacostraca
◦Leptostraca (sea fleas)
◦Stomatopoda (squills)
◦Decapoda (crabs and lobsters)
◦Euphausiacea (krill)
◦Amphionidacea
◦Isopoda (isopods)
◦Amphipoda (sand-hoppers, etc.)
◦Mictacea (mictacids)
◦Tanaidacea (scissor-lice)
◦Cumacea (cumacids)
◦Mysidacea (opossum shrimps or mysids)
Chelicerata
•Pycnogonida (sea spiders)
•Arachnida
Acariformes (sea mites)
Tardigrada (water-bears)
Pentastoma (tongue-worms)
Phoronida (phoronids)
Brachiopoda (lamp-shells)
Bryozoa (sea mats and moss animalcules)
Stenolaemata
Gymnolaemata
Echinodermata (echinoderms)
Crinoidea (feather-stars)
Asteroidea (starfish)
Ophiuroidea (brittle stars)
Echinoidea (sea-urchins)
Holothuroidea (sea-cucumbers)
Chaetognatha (arrow-worms)
Hemichordata (hemichordates)
Enteropneusta (acorn-worms)
Pterobranchia (pterobranchs)
Planctosphaeroidea (planctosphaerids)
Chordata
Urochordata (tunicates)
•Ascidiacea (sea-squirts)
•Thaliacea (pelagic tunicates)
•Appendicularia (appendicularians)
Cephalochordata (lancelets)