lain during the beginning of the last significant sea level rise of the Western Interior Seaway. Sediments deposited during in the formation show that the alluvial channels were flowing to the east or southeast, towards the Bearpaw Sea of the Western Interior Seaway, creating meandering paths as the flow or water down and up during tidal cycles across the floodplain was balancing out. The climate of the environment in the Cretaceous was much different than in present day, being warmer and more temperate, with wet and dry seasons allowing for a large variety of flora and fauna. Periodic areas of standing water would occur in the low-lying plains. Where there was dense vegetation, conifers were the dominant plants, with an understory composed of ferns and tree ferns, and flowering herbs and shrubs. The forest floor was covered by decaying vegetative matter, small ferns, lycopods and angiosperms, mosses, lichens, and fungi, with plentiful algae where there was standing water. The constant presence of water in the Dinosaur Park Formation led many forms of freshwater or marine animals to enter the otherwise predominantly terrestrial ecosystem. In the lower Dinosaur Park Formation, assemblages of crevasse sites show that mollusks were commonly dominated by the freshwater clam Sphaerium, which occurred with abundant gastropods of the genera Goniobasis and Lioplacodes. This sphaeriid-dominated diversity was present during all of the duration of the formation and its over- and underlying deposits, but the mussel and brackish-water assemblages that can be seen in older and younger layers are absent in the range of above the Dinosaur Park Formation-Oldman Formation contact. A variety of forms of fish are present in the fluvial beds of the Dinosaur Park Formation, including chondrichthyans, teleosts and other ray-finned fishes. The ray Myledaphus is characteristic of the formation and similar deposits, and lived alongside the less common shark Hybodus montanensis, intermediate paddlefish and sturgeons, the long, slender fish Belonostomus, the gar Lepisosteus, bowfins, and an abundance of small teleosts including Paratarpon and Cretophareodus. At least nine forms of amphibians were present in the Dinosaur Park Formation, including the salamander-like Albanerpeton, two unnamed forms of frog, and salamanders from the genera Scapherpeton, Lisserpeton, Opisthotriton, Habrosaurus, and two or three unnamed forms. Turtles are commonly well-preserved in the formation, with many taxa known from many specimens. Three genera in the primitive turtle family Baenidae are known, Plesiobaena, Boremys and Neurankylus. The low-domed macrobaenid Judithemys was named