Cretaceous Period, 70 million years BP. A group of two fossilised teeth and one tooth fragment from the marine reptile Plesiosaurus mauritanicus. 66.2 grams total, 8.8-10.3cm (3 1/2 - 4"). From a Cambridgeshire collection. Plesiosaur was a marine reptile predator that roamed the seas during the era of the dinosaurs.