In the middle of the Jurassic, very large Pliosauridae evolved. These were characterized by a large head and a short neck, such as "Liopleurodon" and "Simolestes". These forms had skulls up to three metres (ten feet) long and reached a length of up to and a weight of ten tonnes. The pliosaurids had large, conical teeth and were the dominant marine carnivores of their time. During the same time, approximately 160 million years ago, the Cryptoclididae were present, shorter species with a long neck and a small head.