The spiny-headed worms are parasitic organisms in the phylum Acanthocephala. There are three classes within the phylum and the different species of the worms infect the intestines of dogs, pigs, wild aquatic birds, and New World monkeys.
They also infect intermediate hosts such as cockroaches, freshwater and marine fish, amphipods, and armadillos. The worms are characterized by a cylindrical body, a spiny proboscis, and are notable for their lack of a digestive tract.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.