There are 52 species divided among two orders . The orders are the Acipenseriformes ( sturgeons and paddlefishes ) , and the Polypteriformes ( reedfishes and bichirs ) . There are 52 species divided among two orders , the Acipenseriformes ( sturgeons and paddlefishes ) and the Polypteriformes ( reedfishes and bichirs ) .