Secernentea are the main class of nematodes, characterised by numerous caudal papillae and an excretory system possessing lateral canals. Like all nematodes, they have no circulatory or respiratory system.
The Secernentea contain several significant parasitic species among the Rhabditia and Spiruria. Caenorhabditis elegans, the famous laboratory animal, is one of the many harmless members of the Rhabditia.
Subclasses and orders of Secernentea are:
Some families traditionally considered to be Rhabditida seem to be closer to the Tylenchida. If the Tylenchia are to be maintained as separate, they probably will be included therein. These are also called as Phasmidians as they have the phasmids which are the posterior glandulo sensory and excretory structure.