UK Ammonite Placenticeras
Placenticeras meeki
Pierre Formation
Upper Cretaceous (Campanian)
Meade County, South Dakota
This example of P. meeki has the original shell removed so that the suture pattern is visible in full detail. The shell material was very carefully removed so that there was no abrasion of the sutures. There is no repair or restoration. The specimen is prepared on its original matrix and is a very good display. The ammonite is 7.5 inches across.
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.