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Rhabditophora (from rhabdito-, rhabdite + Greek language -φορος - phoros, bearer, i.e., "rhabdite bearers") is a subphylum (previously a class) of flatworms. It includes all parasite flatworms (clade Neodermata) and most free-living species that were previously grouped in the now obsolete class Turbellaria. Therefore, it contains the majority of the species in the phylum Platyhelminthes, excluding only the Catenulida, to which they appear to be the sister group.
The clade Rhabditophora was originally erected by Ulrich Ehlers in 1985Ehlers, U. (1985) Phylogenetic relationships within the Platyhelminthes. In S. Conway Morris; J. D. George; R. Gibson; H. M. Platt (Eds.), The origins and relationships of lower invertebrates. Oxford, Clarendon Press, p. 143-158. based on morphological analyses and its monophyly was later confirmed by molecular studies.
Another important synapomorphy of the group is the duo-glandular adhesive system. It is a structure of the epidermis containing three different cell types: anchor cells, adhesive glands and releasing glands. The adhesive glands secrete an adhesive substance that attaches the anchor cells to a surface, while the releasing glands secrete a substance able to release the anchor cells from surfaces. This systems allows rhabditophorans to adhere and release quickly from the substrate, even several times in a second.
The secretory organs of rhabditophorans, the nephridium, also have a unique anatomy in which the and tube cells present a series of cytoplasmic projections that overlap, forming a two-cell 'weir'.
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