During the Triassic period sedimentation resumed. The geologic record reveals that South Dakota was moist coastal plain at that time. Seawater once more covered South Dakota during the Jurassic. This sea was home to creatures like ammonites, clams, crinoids, and starfish. As the sea retreated South Dakota became a terrestrial environment dotted with lakes, streams, and swamps. The state was covered again by the sea during the Cretaceous period. This sea was called the Western Interior Seaway.: This sea was home to many invertebrates, aquatic birds, and marine reptiles. The Cretaceous life of South Dakota was similar to that of Wisconsin.: Some of South Dakota's ammonites were very unusual for the group.: During the Late Cretaceous the region now occupied by the Black Hills of South Dakota may have attracted long necked plesiosaurs from hundreds of miles away as a source of gastroliths.: Short-necked plesiosaurs like Dolichorhynchops also lived in the Western Interior Seaway of South Dakota during the Campanian. They were fast swimmers who fed on contemporary small fish and cephalopods. Most short-necked plesiosaurs were relatively small, with body lengths of less than ten feet. However, one South Dakotan individual was long.: More shark species are known from the Cretaceous Western Interior Seaway deposits of South Dakota than other states with rocks from the same environment like those of Kansas.: Otherwise these two states had similar shark communities.: During the Late Campanian, South Dakota was home to the colossal sea turtle Archelon ischyros. The first specimen was long.: Archelon is the largest known turtle in history. Its size is comparable to that of a small car.: Also during the Cretaceous, geologic uplift was forming the Black Hills in the western part of the state. Local dinosaurs included the armored Edmontonia, duck-billed Edmontosaurus, the ostrich dinosaur Ornithomimus, Pachycephalosaurus, Triceratops, and Tyrannosaurus.