"Platypterygius" reached a length of about 7 m (23 ft). It had a long snout and a powerful finned tail. There are more digits in the front flippers than is usual in ichthyosaurs; they are tightly bound in rows, giving a broad, flat appearance. This unusual characteristic gives the genus its name, meaning 'flat wing.' Furthermore, some of the wrist bones have disappeared entirely. CAT scans on a juvenile specimen strongly suggest that "Platypterygius" was deaf.