On the marine sister groups of the freshwater crabs (Crustacea : Decapoda : Brachyura)

Freshwater crab sister group relationships with marine eubrachyuran familie s were investigated. A morphology-based cladistic analysis was conducted on representatives of the freshwater crab families Deckeniidae, Gecarcinucida e, Parathelphusidae, Potamidae, Poramonautidae, Pseudothelphusidae, and Tri chodactylidae using a disparate assemblage of marine heterotreme and thorac otreme brachyurans as possible sister groups. The monophyly of the freshwat er crabs sensu lato is falsified. The family Trichodactylidae and the marin e portunid subfamily Carcininae form basal groups within the superfamily Po rtunoidea. The monophyly of the Pseudothelphusidae and the Paleotropical fr eshwater crab families is supported, and this clade is the sister group of the Thoracotremata (Gecarcinidae, Grapsidae s.l., and Ocypodoidea). The ori gin, groundplan. and diversification of freshwater crabs are discussed in t he context of previously published scenarios of their evolution.