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Acanthocephala (thorny-headed worms) A phylum of bilaterally symmetrical, pseudocoelomate, worm-like organisms most of which do not have an excretory system; all lack a gut. A retractable proboscis is present, covered with the recurved spines that give the animals their common name. All acanthocephalans are endoparasitic, living in two or three marine or terrestrial vertebrates during their development. There are about 600 species.

Acanthocephala

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