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Lower Pennsylvanian (Morrowan) Crinoids from Arkansas, Oklahoma, and Texas

Raymond Cecil MooreHarrell Le Roy Strimple

出版	University of Kansas Paleontological Institute, 1973
URL	http://books.google.com.hk/books?id=APnaKQAACAAJ&hl=&source=gbs_api

註釋"The Lower Pennsylvanian (Morrowan) crinoid fauna is large and notably varied in composition. In the mid-continent region of the United States it is surprisingly short-ranged stratigraphically, being confined in northwestern Arkansas and Northeastern Oklahoma to a few feet of beds in the Brentwood Limestone Member of the Bloyd Formation or their equivalent and in the east-central and southern Oklahoma to the lower part or lower middle part of the Wapanucka Formation, predominantly limestone associated with some shale. The Morrowan crinoids are mostly inadunates, but a few flexible and camerate forms occur with them. This report describes and illustrates only part of the assemblage. As presently known, the Morrowan crinoid fauna contains 45 genera (3 new) distributed among 30 families (4 new); recognized species total 75 (38 new). Several superfamilies are recognized in our classification of Morrowan crinoids. These are defined primarily by 1) dorsal cup shape--longitudinally straight-sided steep to moderately sloped cones, bowl-shaped (crateriform) with concave base--and 2) width of radial articular facets--narrow (angustary), width distinctly but only slightly less than greatest radial width (peneplenary), and fully equal to summit radial width (plenary). Supplemental only are 3) cup anal plates (4 to 1, or none visible externally), 4) nature of anal sac, 5) arm structure (few or many-branched, with isotomous or heterotomous bifurcations, and recti-uniserial, obliqui-uniserial, or biserial arrangement of brachials), and 6) transverse shape of stem and presence or absence of cirri. Finally, we may note that the Morrowan crinoids are linked to succeeding Pennsylvanian and Permian faunas more closely than to Mississippian assemblages of these echinoderms."--Pg. 7.