The eyes of Plioplatecarpus are proportionally larger than those of many mosasaur genus, although the skull is relatively short. It has fewer teeth than most mosasaurs (only about 12, or less), but they are greatly recurved. This suggests that Plioplatecarpus would have hunted relatively small prey that it could grab very precisely.
Plioplatecarpus was first found in Europe by paleontologist Louis Dollo (P.marshi), in 1882. It was relatively incomplete, but more fossils would soon turn up. In North America, Edward Drinker Cope found another mosasaur in 1869, but had identified it as Mosasaurus. It would later be reclassified as Plioplatecarpus, as would Cope's Liodon, in 1870. Liodon would be reclassified as Platecarpus, and later as Prognathodon. However, some have placed it in the genus Plioplatecarpus.
Plioplatecarpus has been found in many locations around the world (most mosasaurs were fairly wide-spread). Pliopltecarpus has been found in the Pierre shale of Kansas, Demopolis Chalk of Alabama, and also in Mississippi, North Dakota, South Dakota, Canada, Sweden, The Netherlands, and, quite recently, Wyoming. The Wyoming specimen is so far the only one of its kind to be found in the state, and may represent a new species of Plioplatecarpus. It is being prepared at the Tate Geological Museum, and has been named Oomtar.