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.
Gigantorhynchida is an order containing a single family, Gigantorhynchidae of Acanthocephala that parasitize vertebrates by attaching themselves to the intestinal wall of their host. There are over 60 species classified into three genera in GigantorhynchidaGigantorhynchus, Intraproboscis, and Mediorhynchus.
Gigantorhynchus is a genus of Acanthocephala that parasitize marsupials, anteaters, and possibly baboons by attaching themselves to the intestines using their hook-covered proboscis. Their life cycle includes an egg stage found in host feces, a cystacanth (larval) stage in an intermediate host such as termites, and an adult stage where cystacanths mature in the intestines of the host. This genus is characterized by a cylindrical proboscis with a crown of robust hooks at the apex followed by numerous small hooks on the rest of the proboscis, a long body with pseudosegmentation, filiform lemnisci, and ellipsoid testes. The largest known specimen is the female G. ortizi with a length of around 240 millimetres (9.4 in) and a width of 2 millimetres (0.08 in). Genetic analysis on one species of Gigantorhynchus places it with the related genus Mediorhynchus in the family Gigantorhynchidae. Six species in this genus are distributed across Central and South America and possibly Zimbabwe. Infestation by a Gigantorhynchus species may cause partial obstructions of the intestines, severe lesions of the intestinal wall, and may lead to death.
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.
Moniliformidae is a family of parasitic spiny-headed worms. It is the only family in the Moniliformida order and contains three genera: Australiformis containing a single species, Moniliformis containing eighteen species and Promoniliformis containing a single species. Genetic analysis have determined that the clade is monophyletic despite being distributed globally. These worms primarily parasitize mammals, including humans in the case of Moniliformis moniliformis, and occasionally birds by attaching themselves into the intestinal wall using their hook-covered proboscis. The intermediate hosts are mostly cockroaches. The distinguishing features of this order among archiacanthocephalans is the presence of a cylindrical proboscis with long rows of hooks with posteriorly directed roots and proboscis retractor muscles that pierce both the posterior and ventral end or just posterior end of the receptacle. Infestation with Monoliformida species can cause moniliformiasis, an intestinal condition characterized as causing lesions, intestinal distension, perforated ulcers, enteritis, gastritis, crypt hypertrophy, goblet cell hyperplasia, and blockages.
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.
Fessisentis is a genus of parasitic spiny-headed worms. It is the only genus in the family Fessisentidae. This genus contains six species that are distributed across the Eastern continental United States as far west as Oklahoma and Wisconsin. These worms parasitize salamanders and fish.
Illiosentidae is a family of parasitic worms from the order Echinorhynchida.
Plagiorhynchidae is a family of parasitic Acanthocephalan worms.
Atactorhynchus is a genus in Acanthocephala which contains two species, A. verecundus and A. duranguensis.
Floridosentis is a genus in Acanthocephala.
Eocollis is a genus in Acanthocephala.
Quadrigyrus is a genus in Acanthocephala.
Gracilisentis is a genus in Acanthocephala.
Neoechinorhynchus is a genus of parasitic worms belonging to the family Neoechinorhynchidae.
Clinostomum is a genus of trematodes in the order Diplostomida.
Mayarhynchus is a monotypic genus of acanthocephalans containing a single species, Mayarhynchus karlae, that infests animals.
Paraechinorhynchus is a monotypic genus of acanthocephalans containing a single species, Paraechinorhynchus kalriai, that infests the rohu.
