- Name Meaning: Without gut
- English Common Name: Acoels
- Major distinguishing characteristics: No mouth or alimentary canal
- Approximate number of species described: unknown
All but two freshwater species are marine. All are aquatic. They live between the grains of sand, in the water column as plankton, or crawling on the substrate or other organisms.
Some consider this group to be a Subphylum of Xenacoelomorpha.
There are two Classes that traditionally belong to the Phylum regardless of their placement.
The Acoelomorpha resemble flat worms. Their internal structures are so simple they have no real internal structures.
The Fossil Record
There is no known fossil record.