The Acoelomorpha are a phylum of animals with planula-like features and formerly considered to be in Platyhelmintha, but recently classified by Jaume Baguñà and Marta Riutort as a separate phylum, basal among the Bilateria. The Acoela are very small flatworms that do not have a gut. Digestion is accomplished by means of a syncytium that forms a vacuole around ingested food. There are no epithelial cells lining the digestive vacuole. All other bilateral animals have a gut lined with epithelial cells. As a result, the acoels appear to be solid-bodied (a-coel, or no body cavity). Acoels are almost entirely marine, living between grains of sediment, swimming as plankton, or crawling on algae. Acoels have a statocyst, which presumably helps them orient to gravity.