Dendrocoelidae

Dendrocoelidae is a family of freshwater tricladida flatworms that has a holarctic distribution. The largest freshwater triclad known belongs to this family, it's up to 40 cm in length and inhabits the Lake Baikal. 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. Dendrocoelidae is the sister group of Kenkiidae. Both families have an anterior adhesive organ, which is considered a synapomorphy of the group. Dendrocoelidae genera known are the following: Phylogenetic supertree after Sluys et al., 2009: