Rotifers are a phylum of animals. They are small bilaterian organisms (ie triploblastic) protostomes leather board measuring 50 microns and 3 mm which often have a trumpet-shaped, cylindrical or spherical. They have two rings of cilia around the mouth and a specialized organ system including a gut.
We now know that the phylum Acanthocephala is actually a group of rotifers become parasites1. The current concept of rotifers (sl) is extended to Acanthocephala and becomes identical to the clade Syndermata.