The flatworms, flat worms, Platyhelminthes, or platyhelminths (from the Greek πλατύ, platy, meaning "flat" and ἕλμινς (root: ἑλμινθ-), helminth-, meaning "worm") are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates. Unlike other bilaterians, they are acoelomates (having no body cavity), and have no specialized circulatory and respiratory organs, which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion (intake of nutrients) and egestion (removal of undigested wastes); as a result, the food cannot be processed continuously.
Platyhelminthes. Retrieved March, 04 2021, from https://en.wikipedia.org/wiki/Flatworm.
Rhabditophora (from rhabdito-, rhabdite + Greek -φορος [-phoros], bearer, i. e. , "rhabdite bearers") is a class of flatworms. It includes all parasitic flatworms (clade Neodermata) and most free-living species that were previously grouped in the now obsolete class Turbellaria. Therefore, it contains the majority of species in the phylum Platyhelminthes, excluding only the catenulids, to which they appear to be the sister group.
Rhabditophora. Retrieved March, 04 2021, from https://en.wikipedia.org/wiki/Rhabditophora.
The Polycladida represents a highly diverse clade of free-living marine flatworms. They are known from the littoral to the sublittoral zone (extending to the deep hot vents), and many species are common from coral reefs. Only a few species are found in freshwater habitats.
Polycladida. Retrieved March, 04 2021, from https://en.wikipedia.org/wiki/Polycladida.
Acotylea is a suborder of free-living marine turbellarian flatworms in the order Polycladida.
Stylochoidea. Retrieved March, 04 2021, from https://en.wikipedia.org/wiki/Acotylea.
Kaburakia excelsa, the giant flatworm or giant leaf worm, is a species of flatworm found on the lower shore and shallow water in the eastern Pacific Ocean. It occurs on the lower shore and shallow sub-littoral zone.
Kaburakia excelsa. Retrieved March, 04 2021, from https://en.wikipedia.org/wiki/Kaburakia_excelsa.