Secernentea

Secernentea was a class 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 This morphological-based classification system has been replaced by the Modern Phylogeny system, where taxonomy assignment is based on small subunit ribosomal DNA (SSU rDNA).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 orders of Secernentea are:


 * Subclass Rhabditia (paraphyletic?)
 * Rhabditida
 * Strongylida
 * Subclass Spiruria
 * Ascaridida
 * Camallanida (sometimes included in Spirurida)
 * Drilonematida (sometimes included in Spirurida)
 * Oxyurida (= Rhabdiasida)
 * Rhigonematida (formerly in Tylenchia)
 * Spirurida
 * Subclass Diplogasteria (may belong in Rhabditia)
 * Diplogasterida
 * Subclass Tylenchia (may belong in Rhabditia)
 * Aphelenchida
 * Tylenchida

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.