Oklahoma Geological Survey Bulletin 1.16, 1984 ATOKAN CRINOIDS

H. L. STRIMPLEl

Abstract-Articulated crinoids are not as prolific in the Atokan Stage as they are in the younger Desmoinesian; however, the Atokan crinoids appear to have closer affinities with them ~han with crinoids of the preceding Morrowan Stage. Conditions for the establishment of widespread "gardens" or "colonies," or for their preservation, were relatively rare in the At~kan. The largest faunas are from the Llano Uplift in north-central Texas, from southwestern MISSOUri, and from Coal County in south-central Oklahoma. Sporadic and limited occurrences of Atokan crinoids are now known from Alaska, northwest­ ern Spain, northern China, Ellesmere Island (Canadian Arctic), eastern Kentucky, Colorado, and New Mexico. Some species reported by Termier and Termier from Morocco are probably of Atokan age, although they are not so recorded. In addition, crinoids from Algeria and the Island of Crete are under study.

INTRODUCTION and Watkins (1969, p. 150) noted the genera in a large crinoid fauna from the Atoka Formation of Conditions were seldom favorable for the pres­ Coal County, Oklahoma, but systematic de­ ervation of crinoids during the Atokan. The first scriptions were not made until later (Strimple, Atokan crinoids appear to have been described by 1975). Tien (1924, 19261, from the Houkou Limestone, Several important occurrences of Atokan cri­ Taiyuan Series of north China (age assignment noids have been reported since 1969. Webster and suggested by Strimple and Watkins, 19691. Lane (1970) reported the occurrence of the camer­ Laudon (1937) described a crown of a flexible cri­ ate crinoid Platycrinites sp., based on dis­ noid with a poorly preserved cup from the Bost­ articulated segments, and described two species of wick Formation of Love County, Oklahoma, which inadunate crinoids from the Atokan part of the he named Synerocrinus farishi. Moore and Strim­ Bird Spring Formation, Arrow Canyon, Nevada. ple (1941) reported Graffhamicrinus granulosus Strimple and others (1971) described three new (as Delocrinus) from the Coody Creek Sandstone crinoid species from the Rainbow Mountain area (Atokan) of northeastern Oklahoma. Strimple and in Alaska, from beds that are considered to be Blythe (1960) described Paragassizocrinus atoka Atokan in age. Strimple and Miller (1971) de­ from the Webbers Falls Sandstone of Cherokee scribed two new species, and reportedParacromy­ County, Oklahoma, and Strimple (1961) described ocrinus marquisi (Moore and Plummer), from the P. eleuatus and P. bulbosus on the basis of in­ Pinkerton Trail Formation near Molas Lake, Col­ frabasal cones and disarticulated plates from the orado, and strongly recommended an Atokan age. Bostwick Formation of Carter County, Oklahoma. Strimple and Nassichuk (1974) reported Calyco­ The status of the latter two species is under study. crinus sp. and two new species from the Hare Fiord Synarmocrinus brachiatus Lane (1964) from the Formation (Atokan) of Ellesmere Island, Arctic Bird Spring Formation of southern Nevada is re­ Canada. Strimple (1976) described two new spe­ portedly of Atokan age. Diphuicrinus patina cies, thought to be Atokan, from the Province of Strimple and Knapp (1966) from the Magofii,n Palencia, northwest Spain. Strimple (1980) re­ beds, Breathitt Formation of eastern Kentucky, IS ported Metacromyocrinus sp., and described two possibly of Atokan age. new species, from the La Pas ada Formation (Ato­ Knapp (1969) reported the first major Atokan kan) ofthe Sangre de Cristo Mountains, New Mex­ crinoid fauna, from the Burgner Formation of J as­ ico. A small faunule from the Island of Crete, per County, Missouri. The Missouri occurrence Greece, is thought to be Atokan in age and is was followed by the Strimple and Watkins (1969) under study, as is another faunule of crinoids from report of crinoids from the Atokan portion of the the Westphalian of Algeria. Marble Falls Formation of San Saba County, Texas and from the Big Saline Formation of PRESERVATION Maso~ County, Texas. These occurrences are in the Llano Uplift of north-central Texas. Strimple Mass mortality accompanied by rapid burial is a prerequisite for the fossilized preservation of a IDepartment of Geology, University ofIowa. Iowa City, "colony" or "garden" of crinoids with attached Iowa.

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