This is a replica fossil of a "stenopterygius skull" of a juvenile icthyosaur. It is an extinct genus of thunnosaur ichthyosaur known from Europe. it is part of the Science Department collection.
Its skull was extended into a kind of a beak and was armed with a quantity of large teeth.
It spent most of its life in the open sea, where it hunted fish and other animals. The abdominal cavity of skeletons of this ichthyosaur often contains the remains of such food. One famous fossil is that of a mother and baby that died in childbirth. This proved that ichthyosaur infants were born tail-first, to prevent them from drowning before fully clearing the birth canal.
Stenopterygius was a very fast swimmer, with a cruising speed similar to that of tuna, which is among the fastest of all living fishes.