The Pennsylvanian Naco Formation of central Arizona has yielded a diverse invertebrate fauna for many years, especially at the Kohls Ranch locality. This locality has become a standard site for student study and amateur collectors, and yields a continuing supply of shallow shelf marine invertebrates, especially brachiopods. Other localities in the Naco Formation yield additional fossils, but none has yielded the diversity or abundance as the Kohls Ranch site. Although crinoids are not the dominant element in the Naco faunas, continued investigation has produced additional specimens of known taxa and an occasional new taxon. Recently discovered specimens provide additional morphologic data, relative abundance information, and paleogeographic relationships with surrounding regions. The arm structure of all crinoid taxa in the Desmoinesian beta member of the Naco Formation of central Arizona places this fauna in the "Terrigenous Facies Belt" of the Midcontinent of the United States. Advanced cladid crinoids, especially cromyocrinids, also show faunal relationships with the Midcontinent faunas and Great Basin faunas but are most comparable to the intermontane basin faunas of the Minturn Formation of Colorado. Naco crinoids are interpreted to have lived in a shallow shelf environment with some clastic influx. Emended descriptions are given for Aglaocrinus konecnyorum, Eirmocrinus brewi, Endelocrinus solus, and Erisocrinus coloradoensis. These new Naco specimens show: anal plate variation in Aglaocrinus konecnyorum and Eirmocrinus brewi; proximal stem structure and range extension for Endelocrinus solus; and the first recognition of Erisocrinus coloradoensis in Arizona.
|Original language||English (US)|
|Number of pages||10|
|State||Published - Jul 2004|
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