Secernentea was a

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 differently ...

of nematodes in the Classical Phylogeny System (Chitwood, 1958) and is no longer in use. This morphological-based classification system has been replaced by the Modern Phylogeny system, where taxonomy assignment is based on small subunit ribosomal DNA (SSU rDNA). Characteristics of Secernentea are: * Amphid apertures are pore/slit-like * Derids are present in some; located near nerve ring * Phasmids are present; posterior * Excretory system is tubular * Cuticle is striated in two to four layers; lateral field is present * Three esophageal glands; esophageal structure varies * Males generally have one testis * Caudal alae are common * Sensory papillae are cephalic only; may be caudal papillae in males * Mostly terrestrial * Rarely found in fresh or marine water

Systematics

Subclasses and

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

s of Secernentea are: Tree of Life Web Project (ToL) (2002)
Nematoda
. Version of January 1, 2002. Retrieved November 2, 2008. * Subclass

Rhabditia Subclass Rhabditia is mostly composed of parasitic nematodes (particularly in the Strongylida), though there are some free-living species as well (particularly in the Rhabditida). Phasmids (posterior sensory structures) are well-developed, whil ...

(paraphyletic?) **

Rhabditida Rhabditida is an order of free-living, zooparasitic, and phytoparasitic microbivorous nematodes living in soil. The Cephalobidae, Panagrolaimidae, Steinernematidae, and Strongyloididae seem to be closer to the Tylenchia, regardless of whet ...

** Strongylida * Subclass

Spiruria Subclass Spiruria comprises mostly parasitic secernentean nematodes. In an alternate classification, they are treated as suborder Spirurina, with the orders listed here being ranked as infraorders. The Ascaridida and the Oxyurida, which includ ...

** AscarididaNickle, W.R. (ed.), (1991). ''Manual of Agricultural Nematology''. New York, NY: Marcel Decker. **

Camallanida The Camallanida are an order of nematodes. * Parasites of terrestrial and aquatic vertebrates * Copepods as obligatory secondary hosts They are sometimes included in the Spirurida as a suborder Camallanina. Notable species and genera *'' ...

(sometimes included in Spirurida) ** Drilonematida (sometimes included in Spirurida) **

Oxyurida Oxyurida is an order of nematode worms of the class Secernentea. It consists of four families, one of which contains the human pinworm (''Enterobius vermicularis''). Species Notable species include: * ''Enterobius vermicularis'', the human p ...

(= Rhabdiasida) ** Rhigonematida (formerly in Tylenchia) **

Spirurida Spirurida is an order of spirurian nematodes. Like all nematodes, they have neither a circulatory nor a respiratory system. Some Spirurida, like the genus '' Gongylonema'', can cause disease in humans. One such disease is a skin infection wi ...

* Subclass

Diplogasteria Diplogasterida was an order of nematodes. It was sometimes placed in a monotypic subclass Diplogasteria, but molecular phylogenetic evidence has shown it to be embedded in the family Rhabditidae (formerly Rhabditina). The confusion of having a ...

(may belong in Rhabditia) **

Diplogasterida Diplogasterida was an order of nematodes. It was sometimes placed in a monotypic subclass Diplogasteria, but molecular phylogenetic evidence has shown it to be embedded in the family Rhabditidae (formerly Rhabditina). The confusion of having a hi ...

* Subclass Tylenchia (may belong in Rhabditia) **

Aphelenchida Aphelenchida is a moderately large order of nematodes. Aphelenchida have a stylet for feeding and a very prominent median bulb in the oesophagus. They are cosmopolitan. Some are associated with insects, and may be ectoparasites or endoparasites ...

Tylenchida Tylenchida is an order of nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant- parasitic nematodes also known as eelworms. They are a ...

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.

References

Protostome classes Obsolete animal taxa {{Secernentea-stub