Abstract

Outcrops of the Niobrara Formation from northwestern Kansas have yielded horizons of well-preserved calcareous nannofossils. Scanning electron and light microscopy have revealed not only several new taxa but also an extraordinary cylindrical coccosphere not previously described from the fossil record. This unusual cylindrical form of a species of Biscutum Black also differs from the characteristic spherical coccosphere by the arrangement of its coccoliths in an ordered and repetitive fashion. A new term “coccocylinder” is proposed here as a more appropriate descriptive term than coccosphere for the cylinder.

A stagnant, anoxic benthic environment prevalent during intervals of Niobrara deposition enhanced the preservation of monospecific coccolith clusters which represent coccospheres that settled to the bottom (often via fecal pellets) before disarticulating. These clusters, representing 34 different species, provide information on the minimum number of coccoliths originally present on the living cell. Such data may be valuable for determining the total biomass of the living populations on the basis of the abundances of individual coccoliths in the fossil record.

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