Chelonians are an ancient family of Anapsid Reptiles, that had shared this world with other animals, for over 245 million years. Back in the Early Triassic Period, the first forms of the Chelonians, where mainly semi-aquatic, small and rather ‘flat’. The iconic rounded shells of later forms, had not yet evolved. Tortoises are expected to have branched off in some forms, into the Turtles, some time in the Late Jurassic. By this time, many of the older Chelonians had become extinct, and the terrestrial Tortoises did not do quite as well under the rule of the Dinosaurs, declining, though surviving. In the oceans, the marine Turtles, had successful integrated themselves into the ecosystems there, and thrived for millions of years. Many were preyed on by large sharks, and most often the giant marine reptiles that would continue to terrorise the seas until the K-T Extinction, 65 million years ago (the same extinction that killed off the Dinosaurs on land) Perhaps the largest marine Chelonian of all time, Archelon, was an immense turtle some 24 feet from flipper-to-flipper, and probably weighed something in the region of 1.5-2 tonnes.