What is "turbellaria"

Turbellaria \Tur`bel*la"ri*a\, n. pl. [NL., dim. fr. L. turbo a whirling.] (Zo["o]l.) An extensive group of worms which have the body covered externally with vibrating cilia. It includes the Rhabdoc[oe]la and Dendroc[oe]la. Formerly, the nemerteans were also included in this group.

n. (context zoology English) Any member of Turbellaria; a flatworm.

The Turbellaria are one of the traditional sub-divisions of the phylum Platyhelminthes (flatworms), and include all the sub-groups that are not exclusively parasitic. There are about 4,500 species, which range from to large freshwater forms more than long or terrestrial species like Bipalium kewense which can reach in length. All the larger forms are flat with ribbon-like or leaf-like shapes, since their lack of respiratory and circulatory systems means that they have to rely on diffusion for internal transport of metabolites. However, many of the smaller forms are round in cross section. Most are predators, and all live in water or in moist terrestrial environments. Most forms reproduce sexually and with few exceptions all are simultaneous hermaphrodites.

The Acoelomorpha and the genus Xenoturbella were formerly included in the Turbellaria, but are no longer regarded as Platyhelminthes. All the exclusively parasitic Platyhelminthes form a monophyletic group Neodermata, and it is agreed that these are descended from one small sub-group within the free-living Platyhelminthes. Hence the "Turbellaria" as traditionally defined are paraphyletic.