What is "protopsephurus"

Protopsephurus is an extinct genus of paddlefish which existed in China during the Barremian age to the Aptian age of the Early Cretaceous period. It contains the species Protopsephurus liui, which was measured to be 7 meters (23 feet) in length, although no weight estimate could be made at the time. It is one of the largest prehistoric Cretaceous freshwater fishes to have ever existed.