Uintacrinus Localities in the Niobrara Formation of Kansas

Abstract

The free-swimming crinoid Uintacrinus Grinnell (1876) has been found in the upper Cretaceous rocks of England, Germany, and the Western Interior region of North America. Grinnell's (1876, p. 81) description was based on specimens from the Uinta Mountains of Utah and the Cretaceous of Kansas. The European example, Uintacrinus westphalicus Schluter (1878), (Zittel, 1913, p. 236) occurs with Marsupites and Bourgeticrinus. Neither Marsupites nor Bourgeticrinus has been found with Uintacrinus in Kansas. In Kansas, Uintacrinus socialis Grinnell normally occurs in great abundance in small areas. Some slabs of approximately 35 square feet have as many as 250 complete individuals represented. Logan (1898, p. 483) described two Uintacrinus slabs, one of which exhibits specimens of adult size; the other has specimens of one-fourth that size and a few near-adult size specimens. The juvenile specimens on the slab mentioned by Logan measure 14 to 35 mm. in diameter. In the fall of 1956 the senior author discovered a small crinoid slab on which the smallest individual measured 35 mm. and the largest measured 65 mm. in diameter. The diameters of the other calices formed a gradation between the two extremes, but most of them measured 55 mm. or larger. The limestone beds containing the crinoid calices are a coquina of crinoid fragments, and usually the slab is one-quarter to one inch thick. The complete calices are on the underside of the slabs when they are in place in the Niobrara formation, and fragments form the remainder of the slabs.