When dinosaurs walked the Earth during the Mesosozic era about 70 million years ago, the shallow seas of the Cretaceous reached north along the Mississippi drainage basin, absorbing rivers from the eroding range of the Appalachian and Smoky mountains, which had once stood mighterier than the Rockies. Some of these sediments are exposed near Adamsville, Tennesse, where gossils from Coon Creek include bones from a mosasaur a carniverous oceanic reptile that grew up to 45 feet long, and many unique shelly fossils that include the offical Fossil of Tennessee: Pterotrigonia thoracica
