Rhabdocoela
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| Rhabdocoela | |
|---|---|
 | |
| Strongylostoma elongatum spinosum. | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Platyhelminthes |
| Subphylum: | Rhabditophora |
| Order: | Rhabdocoela Ehrenberg, 1831 |
| Suborders | |
Rhabdocoela is an order of flatworms in the class Rhabditophora with about 1700 species described worldwide. The order was first described in 1831 by Christian Gottfried Ehrenberg.[1] Most of rhabdocoels are free-living organisms, but some live symbiotically with other animals.[2]
Although Rhabdocoela is a highly supported group in molecular studies, there is no clear morphological synapomorphy that unites them. All rhabdocoels have a bulbous pharynx, but this is shared with other flatworm groups, such as Neodermata, Lecithoepitheliata and some species of Prolecithophora.[3]
Some possibly identified synapomorphies are found in the ultrastructure of the protonephridial system, but similar constructions exist in other groups. Another possible apomorphy is found in the ultrastructure of the sperm, which has a dense heel on the basal bodies during spermiogenesis, but some groups have lost this feature.[3]