Ascaridida Camallanida (disputed) Drilonematida (disputed) Oxyurida Rhigonematida Spirurida Spirurina 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.

Spiruria contains a diverse group of worms that inhabit soil, water, and other bodies of organism.

The subclass of Spiruria has a specialized structure called stoma, which ingests fluid from its host's tissue.

The Camallanida and Drilonematida are sometimes included in the Spirurida as suborder and superfamily, respectively.