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.
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.
Mediorhynchus is a genus of small parasitic spiny-headed worms. Phylogenetic analysis has been conducted on two known species of Mediorhynchus and confirmed the placement along with the related genus Gigantorhynchus in the family Gigantorhynchida. The distinguishing features of this order among archiacanthocephalans is a divided proboscis. This genus contains fifty-eight species that are distributed globally. These worms exclusively parasitize birds by attaching themselves around the cloaca using their hook-covered proboscis. The bird hosts are of different orders.
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.
Oligacanthorhynchida is an order containing a single parasitic worm family, Oligacanthorhynchidae, that attach themselves to the intestinal wall of terrestrial vertebrates.
Arhythmacanthidae is a family of parasitic worms from the order Echinorhynchida.
Cavisomidae are a family of parasitic worms from the order Echinorhynchida.
Pomphorhynchidae is a family of parasitic worms from the order Echinorhynchida.
Leptorhynchoididae 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.
Oligacanthorhynchus is a genus of parasitic worms belonging to the family Oligacanthorhynchidae.
Acanthogyrus is a genus of parasitic worms belonging to the family Quadrigyridae. The species of this genus are found in Africa.
Rhadinorhynchus is a genus of worms belonging to the family Rhadinorhynchidae.
Neoechinorhynchus is a genus of parasitic worms belonging to the family Neoechinorhynchidae.
Pseudoacanthocephalus is a genus of parasitic worms belonging to the family Echinorhynchidae.
Pomphorhynchus is a genus of parasitic worms belonging to the family Pomphorhynchidae.
Porrorchis is a genus of worms belonging to the family Plagiorhynchidae.
Falcaustra is a genus of nematodes belonging to the family Kathlaniidae.
