This study represents the first extensive description of the genus Plioplatecarpus DOLLO 1882, from the Maastrichtian of Belgium and The Netherlands. It is based primarily on holotype and previously undescribed material. Unusual characters of the skull roof, the basioccipital and the jaws and dentition are examined and the character states assessed where possible. A reliable formula for the vertebral column is provided, based on perhaps the most complete Plioplatecarpus known, a specimen of P. houzeaui . Taxonomy, feeding, as well as the alleged behaviour of deep diving, are discussed, contrasting frequently with previous views. The ecology of Plioplatecarpus is mentioned in the light of recent material discovered in Africa and on documentation of the North American P. primaevus . It also takes account of recent information on the use of underwater-flight in P. marshi .