The family
Argulidae contains the
carp lice or
fish lice – a group of parasitic crustaceans of uncertain position within the Maxillopoda. Although they are thought to be primitive forms, they have no fossil record. The Argulidae are the only family in the order
Arguloida (occasionally "Arguloidea"), although a second family, the Dipteropeltidae, has been proposed.
(Wikipedia)