Smoky Hill Chalk Member

Smoky Hill Chalk Stratigraphic range: Upper Cretaceous
This fossil of Toxochelys, an extinct marine turtle, is held in the Smithsonian's National Museum of Natural History. Many Smoky Hill Chalk vertebrate fossils have found their ways to natural history museums all over the world.
Type	Geological formation
Lithology
Primary	Chalk
Location
Region	mid-continental
Country	United States
Type section
Named for	Smoky Hills, Kansas

The Smoky Hill Chalk Member of the Niobrara Chalk formation is a Cretaceous conservation Lagerstätte, or fossil rich geological formation, known primarily for its exceptionally well-preserved marine reptiles. The Smoky Hill Chalk Member is the uppermost of the two structural units of the Niobrara Chalk. It is underlain by the Fort Hays Limestone Member; and the Pierre Shale overlies the Smoky Hill Chalk. The Smoky Hill Chalk outcrops in parts of northwest Kansas, its most famous localities for fossils, and in southeastern Nebraska. Large well-known fossils excavated from the Smoky Hill Chalk include marine reptiles such as plesiosaurs, large bony fish such as Xiphactinus, mosasaurs, flying reptiles or pterosaurs (namely Pteranodon), flightless marine birds such as Hesperornis, and turtles. Many of the most well-known specimens of the marine reptiles were collected by dinosaur hunter Charles H. Sternberg and his son George. The son collected a unique fossil of the giant bony fish Xiphactinus audax with the skeleton of another bony fish, Gillicus arcuatus inside the larger one. Another excellent skeleton of Xiphactinus audax was collected by Edward Drinker Cope during the late nineteenth century heyday of American paleontology and its Bone Wars.