Meiofauna is loosely defined as animals capable of passing through a 0.5-mm mesh. Those associated with various marine sediments include entire phyla (such as kinorhynchs and gastrotrichs), entire major clades of other invertebrate phyla (especially among the arthropods, nematodes, annelids and platyhelminthes), as well as miniaturized representatives of most other animal phyla. Meiofauna probably accounts for well in excess of half the diversity present in complex biotopes such as coral reefs, with most but not all of it associated with sediments.
