This mosasaur skull, Prognathodon overtoni, was collected in October 1980 from Mangahouanga Stream, a tributary of the Te Hoe River, Hawke's Bay, by Joan Wiffen and her husband Pont. It is late Cretaceous in age (around 80 million years ago). Mosasaurs were marine reptiles. Able swimmers, they could chase squid and fish and also preyed upon turtles and ammonites. Ammonites have been found with bite marks where mosasaurs tried to crack them open.

This fossil is part of the GNS Science National Paleontological Collection.