Maastrichtian deposits, the latest Cretaceous, and probably died off due to a cooling trend which other turtles were able to survive due to some thermoregulatory capabilities. Average water temperature may have decreased to depending on estimated CO2 levels. However, some Maastrichtian-age Kansas Pierre Shale fossils may have been eroded millions of years ago, and it is possible Archelon survived well into the Maastrichtian. See also Stupendemys Psephophorus Atlantochelys Largest prehistoric animals References Cited text Further reading Hay, O. P. 1908. The fossil turtles of North America. Carnegie Institution of Washington, Publication No. 75, 568 pp, 113 pl. Wieland, G. R. 1902. Notes on the Cretaceous turtles, Toxochelys and Archelon, with a classification of the marine Testudinata. American Journal of Science, Series 4, 14:95-108, 2 text-figs. External links Oceans of Kansas Paleontology Protostegidae Late Cretaceous turtles of North America Fossil taxa described in 1896 Prehistoric turtle genera Extinct turtles Monotypic prehistoric reptile genera