page_title: Paleobiota of the Niobrara Formation
hierarchical_section_title: Paleobiota of the Niobrara Formation
caption_attribution_description: Pseudoperna congesta (Conrad in Nicollet, 1843) - fossil oysters encrusting a Platyceramus platinus inoceramid bivalve shell in the Cretaceous of Kansas, USA. The light-colored, irregularly-shaped structures shown above are Pseudoperna fossil oysters that are encrusting a portion of a large inoceramid bivalve shell that is eroding from Cretaceous-aged chalk in western Kansas. Inoceramids included the largest clams in Earth history - they are known to have reached about 10 feet in size (for a complete specimen, see: en.wikipedia.org/wiki/Platyceramus#/media/File:Platyceram...). Inoceramids are often described as having a turkey platter morphology - they had large, relatively thin shells that spread out their weight on soft, fine-grained, nonlithified chalk seafloors. Hard-substrate encrusting organisms such as oysters could not occupy such soft seafloors so they preferentially attached to the mineralized biologic surfaces of inoceramids. Classification of encrusting Pseudoperna oysters: Animalia, Mollusca, Bivalvia, Ostreoida, Ostreidae Classification of host inoceramid bivalve: Animalia, Mollusca, Bivalvia, Pteriomorphia, Praecardioida, Inoceramidae Stratigraphy: Smoky Hill Chalk Member (a.k.a. Smoky Hills Member), Niobrara Formation, Upper Cretaceous Locality: Castle Rock chalk badlands, north of Gove County Road K &amp; east of Castle Rock Road, 23 kilometers south-southeast of the town of Quinter, eastern Gove County, western Kansas, USA
context_page_description: During the time of the deposition of the Niobrara Chalk, much life inhabited the seas of the Western Interior Seaway. By this time in the Late Cretaceous many new lifeforms appeared such as mosasaurs, which were to be some of the last of the aquatic lifeforms to evolve before the end of the Mesozoic. Life of the Niobrara Chalk is comparable to that of the Dakota Formation, although the Dakota Formation, which was deposited during the Cenomanian, predates the chalk by about 10 million years.
context_section_description: During the time of the deposition of the Niobrara Chalk, much life inhabited the seas of the Western Interior Seaway. By this time in the Late Cretaceous many new lifeforms appeared such as mosasaurs, which were to be some of the last of the aquatic lifeforms to evolve before the end of the Mesozoic. Life of the Niobrara Chalk is comparable to that of the Dakota Formation, although the Dakota Formation, which was deposited during the Cenomanian, predates the chalk by about 10 million years.
caption: Pseudoperna congesta fossil osyters encrusting a large Platyceramus platinus  bivalve shell, Smoky Hill Chalk member of Niobrara Formation . Photo in place at Castle Rock chalk badlands, Kansas.
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