LOWER MISSISSIPPIAN CRINOIDS FROM UTAH COUNTY, UTAH

Crinoids are reported for the first time from the Lower Mississippian rocks from Santaquin Pole Canyon, Utah County, central Utah. Three crinoids, Nunnacrinus n. sp., Paracosmetocrinus n. sp., and Platycrinites sp., are reported from the Fitchville Formation that ranges in age from Late Devonian to Kinderhookian (Lower Mississippian). Crinoid-bearing strata are dominantly medium-bedded, dark grey carbonate mudstones and wackestones, with rare cross-bedded grainstones. Conspicuous faunal associates are large gastropods, rugose corals, Cladochonus, another tabulate coral, fenestrate bryozoans, brachiopods, and trace fossils. Less common elements of this fauna are disarticulated echinoid plates and sponge spicules. In North America Paracosmetocrinus is confined to Kinderhookian strata, Nunnacrinus is known from early Osagean strata in western North America but from Kinderhookian to middle Osagean strata in the midcontinent, and Platycrinites is a long-ranging taxon. Therefore, these three genera suggest that these crinoid-bearing beds are from the Kinderhookian upper Fitchville Formation in central Utah. Other available biostratigraphic indicators are consistent, although less precise, with this interpretation. This central Utah occurrence of Nunnacrinus extends the geographic and facies range of this genus in western North America. In western North America, Nunnacrinus was previously known only from Osagean waulsortian and waulsortian-associated facies in the Lake Valley Formation of New Mexico.