Phylum: Acanthocephala (Spiny-headed or Thorny-headed Worms)
"Acanthocephalans, also known as thorny-headed or spiny-headed worms, belong to a relatively small group of obligatory endoparasites in the alimentary tract of vertebrates. The length of avian species varies from several millimeters to greater than 10 cm. At adult stages acanthocephalans are gut dwellers. The fixatory organ (proboscis) is deeply inserted into the intestinal wall (Fig. 14-115). Acanthocephalans are diecious with a somewhat hidden sexual dimorphism. Their life cycle is indirect. Eggs excreted with the host's feces contain a larval stage (acanthor) embedded in membranes. Obligate or facultative coprophagic crustaceans and insects serve as intermediate hosts. The acanthor leaves the egg membranes in the gut of the intermediate host and migrates into the body cavity. Here it forms a second larva (acanthella) that later encysts to become a cystacanth. Many acanthocephalan species are known to infect paratenic hosts, and only after being ingested by a suitable final host the larva develop into the adult stage. [With] an estimated 1100 representatives worldwide"
Source: Wernery, Ulrich. (2016). Infectious diseases, pp. 434-521. In: Samour, Jaime (ed.). Avian Medicine, third edition. Mosby Ltd. https://doi.org/10.1016/B978-0-7234-3832-8.00014-6
Class: Archiacanthocephala
Order: Apororhynchida [1 family (Apororhynchidae); 1 genus (Apororhynchus); 7 species]
–No subordinate taxa
Order: Gigantorhynchida [1 family (Giganthorhynchidae); 2 genera (Gigantorhynchus, Mediorhynchus); 64 species]
–No subordinate taxa
Order: Moniliformida [1 family (Moniliformidae); 3 genera (Australiformis, Moniliformis, Promoniliformis); 20 species]
–No subordinate taxa
Order: Oligacanthorhynchida [1 family; 12 genera; 96 species]
Family: Oligacanthorhynchidae
| Scientific Name | Author/s | Common Name | Last Record | Distribution | Status | Taxon Profile |
| Pachysentis gethi | (Machado-Filho, 1950) | Geth's spiny-headed worm | 1950 or before | Brazil (& Mexico?) | Uncertain | Access |
Class: Eoacanthocephala
Order: Gyracanthocephala [1 family (Quadrigyridae); 9 genera; many species]
–No subordinate taxa
Order: Neoechinorhynchida [3 families (Dendronucleatidae, Neoechinorhynchidae, Tenuisentidae); 20 genera; many species]
–No subordinate taxa
Order: Polyacanthorhynchida [1 family (Polyacanthorhynchidae); 1 genus (Polyacanthorhynchus); 4 species]
–No subordinate taxa
Class: Palaeacanthocephala
Order: Echinorhynchida [13 families; many genera; many species]
–No subordinate taxa
Order: Heteramorphida [1 family (Pyrirhynchidae); 1 species (Pyrirhynchus heterospinus)]
–No subordinate taxa
Order: Polymorphida [3 families (Centrorhynchidae, Plagiorhynchidae, Polymorphidae); 23 genera; many species]
–No subordinate taxa
Appendix 1: Possible future additions to this list
The species Acanthogyrus barmeshoori Amin et al., 2013 was described from specimens collected from the host fish Aphanius farsicus (Farsi tooth-carp) during July 2006-June 2007. The host species is now feared extinct in the wild (Esmaeili & Freyhof, 2014).
Statistics
| Conservation status | Number of taxa (in percentage) |
| Extinct | 0 |
| Missing | 0 |
| Extinct in the Wild | 0 |
| Possibly Extinct in the Wild | 0 |
| Globally Rediscovered | 0 |
| Rediscovered in the Wild | 0 |
| Reintroduced | 0 |
| Hypothetical | 0 |
| Invalid | 0 |
| Erroneously listed | 0 |
| Uncertain status | 1 (100%) |
| Total | 1 |