Onychopoda, from Ancient Greek ὄνυχος, meaning "claw", and πούς poús, meaning "foot", are a specialised order of branchiopod crustaceans, belonging to the superorder Cladocera.

Cercopagis pengoi, or the fishhook waterflea, is a species of planktonic cladoceran crustaceans that is native in the brackish fringes of the Black Sea and the Caspian Sea. In recent decades it has sp