Macrostomorpha is a clade of free living flatworms ranked either as

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

or subclass in the group

Rhabditophora 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 groupe ...

. There are about 260 described species in two orders - marine, freshwater and brackish

Macrostomida Macrostomidaevan Beneden, E. 1870. Étude zoologique et anatomique du genre ''Macrostomum'' comprenant la description de deux especes nouvelles. Bulletin de l'Académie Royale des Sciences, des Lettres et des Beaux-Arts de Belgique 30:116-133, on ...

, which group most of the species diversity, and exclusively marine

Haplopharyngida ''Haplopharynx'' is a genus of small, free living marine flatworms found in the North Atlantic and the Mediterranean. It is the only genus in the monotypic family Haplopharyngidae. Species The following species are recognized in the genus ''Hap ...

with only three described species. Macrostomorpha constitute a basal group in Rhabditophora, showing such plesiomorphic condition as entolecithal eggs and spiral cleavage. Another trait found among members of the clade is presence of hard stylet in the male copulatory organ.

References

Turbellaria Rhabditophora {{flatworm-stub