843 J. Paleont., 76(5), 2002, pp. 843–851 Copyright  2002, The Paleontological Society 0022-3360/02/0076-843$03.00 CHEIROCYSTIS FULTONENSIS, A NEW GLYPTOCYSTITOID RHOMBIFERAN FROM THE UPPER ORDOVICIAN OF THE CINCINNATI ARCH—COMMENTS ON CHEIROCRINID ONTOGENY COLIN D. SUMRALL AND GREGORY A. SCHUMACHER Department of Geoscience, University of Iowa, Iowa City 52242-1379, and Geier Collections and Research Center, Cincinnati Museum Center, 1720 Gilbert Ave., Cincinnati, Ohio 45202, Colin-Sumrall@uiowa.edu (Present address: Department of Geological Sciences, University of Tennessee, Knoxville, TN 37996-1410), and Ohio Department of Natural Resources, Division of Geological Survey, 4383 Fountain Square Drive, Columbus 43224, greg.schumacher@dnr.state.oh.us ABSTRACT—A new glyptocystitidoid rhombiferan, Cheirocystis fultonensis, is described from the contact zone between the Point Pleasant Formation and lower Kope Formation exposed 50 km south east of Cincinnati, Ohio. This species, the second known glyp- tocystitidoid rhombiferan from the Cincinnatian Series and the youngest known species of Cheirocystis, shows significant suture modification where pectinirhombs are placed. Growth of large pectinirhombs along vertical sutures results in an unusual bowing-out of thecal plate sutures that is also seen in the related species Cheirocystis anatiformis. A juvenile specimen shows that ontogenetically the lateral shared ambulacra become less pronounced, pectinirhombs are added until the eight standard positions are expressed, and the periproct becomes proportionately smaller with age. INTRODUCTION G LYPTOCYSTITIDOID RHOMBIFERANS are a small but successful clade of blastozoan echinoderms whose geological range is Late Cambrian through Late Devonian. Although common and di- verse at some localities in North America—e.g., the Keyser For- mation (Schuchert, 1904), the Bromide Formation (Sprinkle, 1982)—they have proven to be rare in the Cincinnatian Series. Formally described Cincinnatian glyptocystitidoids include only the well-known callocystitid Lepadocystis moorei (Meek, 1871; Jaekel, 1899; Bather, 1899; Foerste, 1914b; Regne ´ll, 1945; Kesling and Mintz, 1961; Sumrall and Sprinkle, 1999) that occurs in the Rich- mondian (Upper Ordovician) Whitewater Formation and Elkhorn Formation northwest of Cincinnati, Ohio. A second glyptocystiti- doid was first illustrated as undetermined cystoid plates from the Rogers Gap Formation (uppermost Point Pleasant Formation equiv- alent) in central Kentucky (McFarlan and Freeman, 1935, pl. 185, fig. 2). Charles Faber intended to describe these plates about this time, labeling several small slabs covered with cheirocrinid plates in his collection (now on reposite at Cincinnati Museum Center) as ‘‘Glyptocystites fultonensis, Faber, (MS.) Cheirotypes’’—i.e., specimens intended to be the type series of a species that was never published. This suggests that Faber either wrote or planned to write a manuscript on these plates that apparently was never published. G. W. Sinclair borrowed these cheirotypes in 1952; Sinclair sug- gested that they were Cheirocrinus rather than Glyptocystites as noted in the collection catalogue. Based on the box labels, Caster et al. (1955) in the revision of Bucher et al. (1939) called these plates Glyptocystites fultonensis and illustrated a single plate (p. 2, fig. 22) describing it in the figure caption as, ‘‘Cystoid plate. Note hexagonal ridges. Complete animal unknown. Common in Eden and Maysville, exact range unknown.’’ We have been unable to replicate the Maysvillian occurrence, but several stems of the ab- errant crinoid Anomalocrinus from Maysvillian strata in the collec- tion at Cincinnati Museum Center are labeled as cystoid stems perhaps accounting for the Maysvillian age assignment. In 1985, G. A. Schumacher collected a large slab of limestone from the upper Point Pleasant Formation along Bullskin Creek in Ohio bearing several largely covered and flattened specimens, in- cluding an exquisite summit with brachioles, which renewed ef- forts to formally describe this species. In 1999, C. E. Brett un- covered a large number of slabs containing isolated thecal plates about 60 cm above the Point Pleasant–Kope contact. Later that year one complete and several partial specimens were collected at a small road-cut near Brooksville, Kentucky, that preserve in- formation on nearly every anatomical detail indicating that this animal belongs within the genus Cheirocystis. LOCALITIES AND STRATIGRAPHY In recent years, several complete and many partial specimens of Cheirocystis fultonensis n. sp. have been collected from a sin- gle location in Ohio and a second location 7 km to the southwest in Kentucky (Fig. 1). The first locality is along Bullskin Creek in Brown County, Ohio, approximately 30 m upstream from the Clermont–Brown County line. A large slab of megarippled cri- noidal grainstone preserved in a small shale pocket at its base several complete specimens. The specimens are fully articulated but flattened, except for an uncrushed articulated summit of one specimen (Fig. 2.1). This slab was eroded and transported a short distance downstream from one of four megarippled crinoidal grainstone beds exposed in Bullskin Creek (Fig. 3). The mega- rippled beds occur in the top meter of the Point Pleasant Member of the Cynthiana Formation (Weiss et al., 1965) or the Point Pleas- ant Formation (Osborne et al., 1973; Schumacher, 1994). The second locality is a road-cut along Kentucky Route 1159 just south of the Alexandria to Ashland (A–A) Highway (Ky. Rt. 9) at the exit for Brooksville, Kentucky. Several complete or par- tial specimens of Cheirocystis fultonensis were collected from several crinoidal grainstone beds within the upper two meters of the Point Pleasant Formation (Outerbridge, 1971; Algeo and Brett, 1999) or the equivalent Point Pleasant tongue of the Clays Ferry Formation (Schumacher et al., in press). Although partly crushed, these specimens preserve details of the thecal interior, including the morphology of the dichopore folds (Fig. 2.2). Additional specimens of Cheirocystis fultonensis were collected at the same road-cut along a single echinoderm-rich horizon in the basal Kope Formation (Outerbridge, 1971; Schumacher et al., 2002; Algeo and Brett, 1999) about 60 cm above the underlying Point Pleasant Formation. A complete, superb uncrushed specimen (Fig. 2.12–2.17) and several other complete and partial specimens were found weath- ered from the shale at the first location. A fully articulated stem and two partial specimens were collected from a thin limestone bed 20 m south at nearly the same stratigraphic interval. At both localities, we have looked for additional Cheirocystis fultonensis specimens from the underlying Point Pleasant For- mation and in the overlying Kope Formation without success.