Horn corals are much scarcer in the older Pennsylvanian (Missourian) strata of the Missouri Series that are exposed along the Missouri River in Washington County and in the lower Platte River Valley of Saunders, Cass and Sarpy counties, Nebraska than they are in the younger (Virgilian) strata. Rocks of Missourian age are exposed in southwestern Iowa and southeastern Nebraska and an extensive outcrop belt of them stretches from near Kansas City and reaches as far south as Tulsa., Oklahoma.
Geyerophyllum patulum Cocke is a fairly rare species of coral. Cocke (1970) recorded only several specimens from the Winterset Limestone in Kansas and stated that none had been found in the northern outcrop belt of Missourian strata he had studied. Since then, several specimens have been recorded from the Winterset Limestone in extreme southwestern Iowa and southeastern Nebraska.
The corallite of Geyerophyllum patulum is usually very shortened and may be of greater diameter than height. The specimens from Nebraska and Iowa have generally been found in a shaly facies in the Winterset Limestone. Probably none have been found in their living position.
Description: Lateral view of "Geyerophyllum patulum" Cocke, 1970. Note that the diameter of the coral is greater than its' height.
Description: View of calyx of "Geyerophyllum patulum" Cocke, 1970.