Platyzoa families

Mesognathariidae is a family of worms belonging to the order Bursovaginoidea.

Haplognathiidae is a family of worms belonging to the order Filospermoidea.

Onychognathiidae is a family of worms belonging to the order Bursovaginoidea.

Pterognathiidae is a family of worms belonging to the order Filospermoidea.

Gnathostomulidae is a family of worms belonging to the order Bursovaginoidea.

Austrognathiidae is a family of worms belonging to the order Bursovaginoidea.

Agnathiellidae is a family of worms belonging to the order Bursovaginoidea.

Chaetonotidae is a family of gastrotrichs in the order Chaetonotida. It is the largest family of gastrotrichs with almost 400 species, some of which are marine and some freshwater. Current classification is largely based on shape and external structures but these are highly variable. Molecular studies show a high level of support for a clade containing Dasydytidae nested within Chaetonotidae.

Dasydytidae is a family of gastrotrichs in the order Chaetonotida.

Clausognathiidae is a family of worms belonging to the order Bursovaginoidea.

Gnathostomariidae is a family of worms belonging to the order Bursovaginoidea.