Abstract

The pelecypods of the Missouri Snyder Creek Shale make up one of the largest and most significant occurrences of this group of molluscs in North American Upper Devonian rocks outside the Appalachian region. This study revises the systematics of the 475 known specimens of Snyder Creek pelecypods and shows that they represent 14 species and 9 genera. The fauna is strongly dominated by the genus Paracyclas, which is unknown in the Appalachian Upper Devonian, but all other Snyder Creek species also occur in the New York standard section for the Late Devonian. The known stratigraphic distribution of the Snyder Creek species in New York suggests that the formation correlates with the low Chemung stage of the Appalachian Upper Devonian standard. Most Snyder Creek pelecypod specimens are preserved as articulated internal or composite molds and many reveal morphological features which are unknown on more poorly preserved Appalachian specimens.

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