Mauisaurus
With 68 cervical vertebrae, Mauisaurus had one of the longest necks of any plesiosaur. It was large, over  in length. Like other plesiosaurs, it had a long slender body, with numerous vertebrae, allowing flexible movement. On its underside, Mauisaurus had two sets of large flippers. These aided in swimming at high speeds, but may have also allowed the plesiosaur to venture onto shorelines for short amounts of time. Mauisaurus was a carnivore, with sharp jagged teeth that would have been used to grip fish or squid.