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 differentl ...

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 This morphological-based classification system has been replaced by the Modern Phylogeny system, where taxonomy assignment is based on small subunit ribosomal DNA (SSU rDNA).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 d ...

s of Secernentea are:

Tree of Life Web Project The Tree of Life Web Project is an Internet project providing information about the diversity and phylogeny of life on Earth. This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The site h ...

(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, while ...

(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 The Strongylida suborder includes many of the important nematodes found in the gastrointestinal tracts of ruminants, horses, and swine, as well as the lungworms of ruminants and the hookworms of dogs and cats. Taxonomy This suborder includes ( ...

* 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 include ...

Ascaridida The order Ascaridida includes several families of parasitic roundworms with three "lips" on the anterior end. They were formerly placed in the subclass Rhabditia by some, but morphological and DNA sequence data rather unequivocally assign them t ...

Nickle, 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 ...

(= 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 with ...

* 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 h ...

* 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 endoparasit ...

Tylenchida Tylenchida is an order of nematodes. List of families * Superfamily Criconematoidea ** Family Criconematidae ** Family Tylenchulidae * Superfamily Tylenchoidea ** Family Anguinidae ** Family Belonolaimidae ** Family Dolicho ...

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