Catenulida

Catenulida is an order of flatworms in the classical classification, or a class of flatworms in a phylogenetic approach. They are relatively small free-living flatworms, inhabiting freshwater and marine environments. There are about 100 species described worldwide, but the simple anatomy makes species distinction problematic.

Stenostomidae is a family of freshwater catenulid flatworms. It is the most species-rich family of catenulids, with about 70 species described, most of them in the Neotropics.

Catenulidae is a family of freshwater catenulid flatworms.

Paracatenula is a genus of millimeter sized free-living marine gutless catenulid flatworms.