Quadrigyridae is the only family within Gyracanthocephala, an order of parasitic worms of class Eoacanthocephala. This family contains two subfamilies, ten genera and about 92 species.
Acanthocephalus is a genus of parasitic worms. One of the species in this genus is Acanthocephalus anguillae, a fish parasite. Acanthocephalans are also found in humans and primates, causing a common zoonotic infection called "human acanthocephaliasis". While pathogens can be transferred among animals and humans, the main source of human acanthocephaliasis is the diet of infected raw fish and insects. Because they are lacking circulatory, respiratory, and digestive systems, Acanthocephalus are exceptionally well-adapted to a symbiotrophic existence.
The thorny-headed worm family Polymorphidae contains endoparasites which as adults feed mainly in fish and aquatic birds. When this taxon was erected by Meyer in 1931, a subfamily Polymorphinae was established in it. As the Polymorphidae as presently understood would then be monotypic, with no basal genera outside the Polymorphinae, the proposed subfamily is redundant for the time being and therefore most modern treatments simply omit it. Polymorphus minutus is an economically significant parasite in goose and duck farming.
Echinorhynchus is a genus of acanthocephalan parasitic worms. They parasitize a wide variety of fishes from both marine and fresh waters. The intermediate host is usually a crustacean.
Centrorhynchidae is a family of parasitic worms. Three species of these thorny-headed worms in the genus Centrorhynchus were found to parasitize birds of prey and owls Slovakia. These hosts include Buteo buteo, Buteo rufinus, Falco tinnunculus, Asio otus, Strix aluco, Strix uralensis and Tyto alba.
Arhythmacanthidae is a family of parasitic worms from the order Echinorhynchida.
Cavisomidae are a family of parasitic worms from the order Echinorhynchida.
Heteracanthocephalidae is a family of parasitic worms from the order Echinorhynchida.
Illiosentidae is a family of parasitic worms from the order Echinorhynchida.
Rhadinorhynchidae is a family of parasitic worms from the order Echinorhynchida.
Plagiorhynchidae is a family of parasitic Acanthocephalan worms.
Polymorphus is a genus of parasitic worms from the phylum Acanthocephala. This group uses amphipod crustaceans as intermediate hosts and various birds as final hosts.
Gorgorhynchus is a genus of worms belonging to the family Rhadinorhynchidae.
Rhadinorhynchus is a genus of worms belonging to the family Rhadinorhynchidae.
Pseudoacanthocephalus is a genus of parasitic worms belonging to the family Echinorhynchidae.
Cryptogonimidae is a family of trematodes belonging to the order Plagiorchiida.
Hemiuridae is a family of trematodes belonging to the order Plagiorchiida containing 514 described species.
Bothriocephalus is a genus of flatworms belonging to the family Bothriocephalidae.
Tegorhynchus is a genus of worms belonging to the family Illiosentidae.
Falcaustra is a genus of nematodes belonging to the family Kathlaniidae.
