Animals in the phylum Kinorhyncha are microscopic marine invertebrates that live in sediment on the ocean floor. They are segmented animals with spiny plates covering their bodies and are known for their retractable heads.

* Acoelomorpha * Platyhelminthes (flatworms) * ** Cestoda (tapeworms) ** Trematoda (flukes) ** Monogenea ** Turbellaria (planarians) * Acanthocephales * Kinorhyncha (mud dragons) * Annelida (segmented worms ) * ** Polychaeta ** Oligochaeta ** Hirudinida (leeches) * Nemertea(ribbon worms ) * Echiura (spoon worms ) * Sipuncula(peanut worms ) * Nematoda (roundworms) * Nematomorpha (horsehair worms or gordian worms ) * Priapulida (penis worms ) * Gnathostomulida (jaw worms )

* Oligochaeta annelids hide in the soil or in the sand. * Polychaeta annelids hide in the sand or inside their shell (the ones who have a shell). * Hirudinidaannelids (leeches) hide under stones and plants. * Kinorhyncha (mud dragons), gnathostomulida(jaw worms), sipunculida (peanut worms) and echiura(spoon worms) hide in the sand. * Turbellaria flatworms, priapulida (penis worms) and nemertea (ribbon worms) hide in the sand and under stones.

There are four different classes of Aschelminthes. Each class has its own examples.

Class Nematoda:

--Ascaris

--Wuchereria

--Trichinella

Class Nematormopha:

--Gordious

--Paragoradium

Class Rotifera:

--Philodina

--Brachionus

Class Gastrotricha:

--Turbanella

--Chaetonotus

Class Kinorhyncha:

--Echinoderes

--Centroderes

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