The family Dendrocoelidae is characterized by an unusual arrangement of the muscle layers of the pharynx. While in most planarians the inner musculature of the pharynx is composed of two muscle layers, one circular and one longitudinal, in Dendrocoelidae the circular and longitudinal fibers are intermingled, forming a mixed layer.
The following genera are recognised in the family Dendrocoelidae:
Phylogenetic supertree after Sluys et al., 2009:Tricladida Continenticola Planarioidea
The largest freshwater triclad known belongs to this family, it's up to 40 cm in length and inhabits the Lake Baikal.