Placenticeras meeki
Pierre Formation
Upper Cretaceous (Campanian)
Meade County, South Dakota

This example of P. meeki has very colorful red and green iridescence in the preserved original aragonite shell. There are several thin spots in the shell and excellent sutures are visible, There are several limpet scars. The specimen is free of matrix and both sides are excellent. The inner-most whorl is restored. There is no repair.

Placenticeras meeki is distinguished by its smooth convex, broad, nearly unornamented flanks and smooth venter. Some specimens ocassionally possess small tubercles along the umbilical shoulder and some slight, broad, low ribbing. P. meeki has a large size range up to 80 cm in diameter. the narrow concave venter is the smaller specimens becomes more rounded in larger shells. The species is rare in the Exiteloceras jenneyi Zone and is abundant in the Didymoceras cheyennense through Baculites cuneatus Range Zones throughout marine Cretaceous deposits of the Western Interior.