Gecarcinucidae

The Gecarcinucidae are a family of true freshwater crabs. They are found throughout South Asia, Southeast Asia and New Guinea, with a single genus found in Australia.

Taxonomy
The family Parathelphusidae is now demoted to the rank of subfamily, as the Parathelphusinae, within the Gecarcinucidae. "Family" Parathelphusidae is now considered as a junior synonym.

The Gecarcinucidae are thought to have originated in the Indian subcontinent when it was an island continent in the Paleogene, despite not being of ancient Gondwanan origins themselves (unlike other lineages that are thought to have originated in Insular India). Divergence estimates indicate that the Gecarcinucidae originate from Southeast Asian ancestors that dispersed to India during the middle Eocene, before India collided with Asia. This is thought to have occurred due to India drifting close enough to Southeast Asia to allow for biotic exchange between both regions. As the Gecarcinucidae are a freshwater group that could not disperse via marine habitats, this indicates that temporary land bridges may have formed in the Eocene between India and Southeast Asia, allowing for the dispersal of freshwater organisms to India while it was still isolated. Following the India-Asia collision, the Gecarcinucidae dispersed back into mainland Asia, and from there to Australasia.

The Gecarcinucidae are thought to be the sister group to the Potamoidea (the superfamily comprising the Potamidae and Potamonautidae).