5, see text The suborder Ascaridina contains the bulk of the Ascaridida, parasitic roundworms with three "lips" on the anterior end.

The Ascaridida were formerly placed in the subclass Rhabditia by some, but morphological and DNA sequence data rather unequivocally assigns them to the Spiruria.

[1] These "worms" contain a number of important parasites of humans and domestic animals, namely in the superfamily Ascaridoidea.

Some paleoparasitological studies have described groups belonging to Ascaridina infecting fish, reptiles, and mammals in the Mesozoic.

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