Acanthocephala (Spiny-Headed Worm)

Members of the phylum Acanthocephala are entirely endoparasitic, but when compared to other invertebrate parasites such as the roundworms (phylum Nematoda) and tapeworms (phylum Platyhelminthes, class Cestoda), they are relatively rare. However, acanthocephalans have succeeded by infiltrating niches within every vertebrate class..