Introverta
Quick Summary
The phylum Introverta is a group of animal phyla characterized by a spiny, retractable proboscis at the head of a wormlike body. This proboscis functions in burrowing through soft substrates or in the guts of hosts. Introverta species are found in both marine and freshwater environments and can be predators or parasites. Parasitic forms often lack a digestive system. The phylum includes approximately 900 species and has existed from the Cambrian period to the present. The phylum Introverta contains the classes Kinorhyncha, Loricifera, Priapulida, and Acanthocephala.12
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