Acanthocephala

The Acanthocephala (Greek ακανθος, akanthos, thorn + κεφαλη, kephale, head) is a phylum of parasitic worms known as acanthocephales, thorny-headed worms, or spiny-headed worms, characterised by the presence of an evertable proboscis, armed with spines, which it uses to pierce and hold the gut wall of its host. Acanthocephalans typically have complex life cycles, involving a number of hosts, including invertebrates, fishes, amphibians, birds, and mammals. About 1150 species have been described.ClassesArchiacanthocephala
Palaeacanthocephala
Eoacanthocephala