Acoelomorpha

Acoelomorpha is a subphylum of very simple and small soft-bodied animals with planula-like features that live in marine or brackish waters. They usually live between grains of sediment, swimming as plankton, or crawling on other organisms, such as algae and corals. Except for two acoel freshwater species, all known acoelomorphs are marine.

== Systematics == === Etymology === The term "acoelomorph" derives from the Ancient Greek words (), the alpha privative, expressing negation or absence, (), meaning "cavity", and (), meaning "form". This refers to the fact that acoelomorphs have a structure lacking a fluid-filled body cavity.