SYSTEMATIC REVIEW OF CRINOID GENERA FROM THE EARLY MISSISSIPPIAN LAKE VALLEY FORMATION (NUNN MEMBER) OF SOUTH-CENTRAL NEW MEXICO

The Nunn Member (Early Osagean) of the Lake Valley Formation of New Mexico has been noted for its abundance of crinoids. Although the formation was first described in the late 1800’s, there has been no comprehensive study on its crinoids, and no complete list of the crinoid genera exists. Webster’s Crinoid Index (2003) includes 21 genera that have been reported in the literature, but this is far from inclusive. Study of the Macurda collection from the University of Michigan, the Laudon collection from the University of New Mexico, and what was personally collected in the field has provided more than 7000 specimens to be examined. An initial examination of these collections indicates that 6 genera previously reported are absent and that at least 20 additional genera are present. Most of the additional genera are from better definition and splitting of some genera, such as Platycrinites and Actinocrinites, and the large sample size available for study. An update of the crinoid genera found in the Lake Valley Formation will allow for a better understanding and easier correlation of crinoid faunas across North American during the Early Mississippian.

Crinoids reported from the Lake Valley Formation found in the collections include the camerates Cactocrinus, Cribanocrinus, Displodocrinus, Dorycrinus, Eretmocrinus, Eutrochocrinus, Nunnacrinus, Physetocrinus, Platycrinites, Rhodocrinites, and Steganocrinus and the cladids Coeliocrinus, Costalocrinus, Cyathocrinites, and Springericrinus. Crinoids reported but not found in these collections include the camerates Cusacrinus, Cytidocrinus, Megistocrinus, Strimplecrinus, and Uperocrinus and the flexible Wachsmuthicrinus. Additional genera found during this study include the camerates Abatocrinus, Agaricocrinus, Ancalocrinus, Aryballocrinus, Blairocrinus, Collicrinus, Dichocrinus, Gilbertsocrinus, Elegantocrinus, Eucladocrinus, Laticrinus, Oenochoacrinus, Plemnocrinus, and Pleurocrinus, the cladids Barycrinus, Cercidocrinus, Holcocrinus, and Pellecrinus, the disparid Synbathocrinus, and the flexible Onychocrinus. These additions show there is still much to learn from the Lake Valley Formation and its significance in understanding crinoid environmental preferences and evolution during the Early Osagean.