Cheyenne River in Custer County (Cretaceous of the United States)

Where: Custer County, South Dakota (43.5° N, 103.1° W: paleocoordinates 49.4° N, 71.0° W)

• coordinate based on nearby landmark

• outcrop-level geographic resolution

When: Pierre Shale Formation, Late/Upper Campanian (83.5 - 70.6 Ma)

• upper Pierre; Prognathodon overtoni found 100 ft above Mosasaurus horridus

• bed-level stratigraphic resolution

Environment/lithology: marine; shale

• "Like most specimens from the Pierre Cretaceous it was enclosed originally in a hard, nodular matrix of a bluish color, from which the larger part of the skull had gradually been oxidized, leaving the bones in the utmost perfection."

Size class: macrofossils

Preservation: concretion

Collected by University of Kansas Geological Expedition in 1894

• Prognathodon overtoni found by T. R. Overton

Primary reference: S. W. Williston. 1895. New or little known extinct vertebrates. Kansas University Quarterly 3(3):165-176 [M. Carrano/H. Street]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 107780: authorized by Matthew Carrano, entered by Hallie Street on 15.04.2011

Creative Commons license: CC BY (attribution)

Taxonomic list

 Squamata - Mosasauridae
"Mosasaurus horridus n. sp." = Mosasaurus missouriensis, Prognathodon overtoni n. sp.
"Mosasaurus horridus n. sp." = Mosasaurus missouriensis Harlan 1834 mosasaur
KU 1034, skull
Prognathodon overtoni n. sp. Williston 1897 mosasaur
KU 950 - type (skull)