The Caryophyllideans are a group of tapeworms that infect fish and annelids (segmented worms) with a simple scolex or "head."

Caryophillideans represent a unique type of tapeworm, such that they possess a monzoic, unsegmented, body, with only a single set of reproductive organs.

[1] In the Caryophyllidean life cycle, adults live in fish, who pass the tapeworm eggs in their feces.

Catfish, suckers, and minnows are among the fishes that can serve as definitive hosts.

The genus Archigetes Leuckart, 1878,[2] a caryophyllidean, is unique among all tapeworms in that its species can mature in invertebrate hosts (Oligochaeta), i.e. have a monoxenic (direct) life cycle.