J. Paleont., 84(5), 2010, pp. 783–794 Copyright ’ 2010, The Paleontological Society 0022-3360/10/0084-0783$03.00
THE SYSTEMATICS OF A NEW UPPER ORDOVICIAN EDRIOASTEROID PAVEMENT FROM NORTHERN KENTUCKY COLIN D. SUMRALL Department of Earth and Planetary Sciences, University of Tennessee, Knoxville 37996, ,
[email protected].
ABSTRACT—A large, edrioasteroid-bearing hardground surface from the base of the Bellevue Member of the Grant Lake Formation near Maysville, Mason County, Kentucky is described. Four species are represented including Streptaster vorticellatus (Hall), Carneyella ulrichi Bassler and Shideler, Carneyella pilea (Hall), and Curvitriordo stecki n. sp. Specimens of S. vorticellatus and C. pilea add little to the known morphologies of these species. However, prior to this study C. ulrichi was known from the unique holotype, and Curvitriordo stecki n. sp. adds greatly to out understanding of Curvitriordo which was previously known from two species comprising three poorly preserved specimens. Curvitriordo stecki shows a bimodal size frequency distribution suggesting seasonal breeding whereas Carneyella ulrichi shows a left skewed size frequency suggesting low juvenile mortality. Streptaster vorticellatus shows a tight unimodal size frequency distribution suggestive of a single spat fall accumulation.
INTRODUCTION
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the upper Ordovician strata around Cincinnati, Ohio are locally common on hard substrates such as shell pavements and hardgrounds and have been known from the area for a century and a half. Recently a new hardground was collected from the base of the Bellevue Member of the Grant Lake Formation near Maysville, Mason County, Kentucky that was covered by a population of 257 specimens of edrioasteroids including some rare species. Most common on the surface represented by 48.6 percent of the specimens is Carneyella ulrichi Bassler and Shideler, in Bassler, 1936, that was previously known from only the holotype. This species is morphologically similar to the well-documented Carneyella pilea (Hall, 1866), but differs in having the surface covered by very large nodes (Bell, 1976a). The second most common species represented by 47.0 percent of the specimens is Curvitriordo stecki n. sp. This is the third known species of the genus that was previously known from three specimens assigned to two species (Bell, 1976a). These specimens are all very poorly preserved, thus C. stecki adds greatly to our understanding of the genus. The third species represented by 3.5 percent of the specimens is Streptaster vorticellatus (Hall, 1866). Interestingly specimens of this species are all very large with an average thecal diameter of 21.3 mm and add to our knowledge of the morphology of large individuals of this genus. A fourth species, Carneyella pilea, is a common and well-known taxon, but is represented on the Maysville hardground by only two specimens amounting to 0.8 percent of the specimens. The assemblage of edrioasteroids found on the Maysville hardground is similar to other edrioasteroid occurrences in and around the Cincinnati region. Maysvillian aged occurrences including the Frishe’s Big Boy locality (Kesling and Mintz, 1960), the Florence 1, and Blue Rock pavements (Meyer, 1990) all contain three edrioasteroid species including Isorophus cincinnatiensis (Roemer, 1851), Carneyella pilea, and Streptaster vorticellatus. Other localities including the Sharonville fossil park surface in the Miamitown Shale is similar though lacking Streptaster (Roberts et al., 2006). Although the Maysville hardground is taxonomically different, the gross ecology of these edrioasteroids is probably very similar. Carneyella ulrichi Bassler and Shideler is nearly identical to C. pilea differing only in the presence of nodes over the surface. Similarly Curvitriordo stecki n. sp. is similar to DRIOASTEROIDS IN
Isorophus cincinnatiensis differing in the presence of tertiary cover plates but is otherwise morphologically very similar. Ecologically, the greatest difference is the substrate. All other described middle Cincinnatian edrioasteroid occurrences are associated with shell pavements typically interpreted as accumulations of dead shells (Meyer, 1990; but see Meyer and Dattilo, 2008; Dattilo et al, 2009). Conversely, the Maysville occurrence is a hardground with edrioasteroids attached to either the surface or encrusting organisms covering the surface. This paper will explore the systematics and ontogeny of these edrioasteroids species. A separate paleoecology paper (Sumrall et al., 2001) published preliminary results and a more in depth report will be published elsewhere. PREVIOUS INVESTIGATIONS
Two of the four species recovered on the Maysville Slab are well-known taxa from the Upper Ordovician of the Cincinnati, Ohio region. Streptaster vorticellatus is known from nine specimens on the slab plus one from float (Fig. 1). These specimens conform well to large specimens most recently detailed by Bell (1976a) albeit all are at the upper range of size for the species. Likewise, the two specimens of Carneyella pilea on the Maysville hardground conform well to the description most recently made by Bell (1976a) and add little to the understanding of the species. Carneyella ulrichi was previously known from a single specimen housed in the US National Museum. This specimen is large and complete, and taphonomically been slumped toward the D ambulacrum, but is otherwise in good condition. Moreover, because this specimen was previously unique, no information was available concerning within population variability or ontogeny. The 125 specimens of Carneyella ulrichi on the Maysville slab provide great insight on these subjects. They show that the distribution of nodes across the surface is very conservative both between specimens and across ontogeny. A number of edrioasteroid beds have been reported previously from the Cincinnatian of the Cincinnati Arch region (Kesling and Mintz, 1960; Meyer, 1990; Datillo, 1998; Goad et al., 2006; Roberts et al., 2006). However, the Maysville occurrence is distinct from the others in several aspects. Most previously reported edrioasteroid occurrences have been derived mainly from the Miamitown and Corryville shaley intervals, which lie respectively slightly below and
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FIGURE 1—Map showing the distribution of edrioasteroids on the surface of the Maysville slab. Note that the edrioasteroids are not randomly distributed. Specimen density for the observed portion of the hardground is as follows: Carneyella ulrichi, 12.1 specimens/m2; Carneyella pilea, 0.2 specimens/m2; Streptaster vorticellatus, 0.9 specimens/m2; Curvitriordo stecki 11.7, specimens/m2; total density 25.0 specimens/m2. Inset shows map of the locality where the edrioasteroid specimens were collected.
SUMRALL—ORDOVICIAN EDRIOASTEROIDS above the present horizon. These assemblages were dominated by the edrioasteroids Isorophus, and Carneyella while Streptaster occurs only very rarely. Curvitriordo is absent from these faunas. Previously described Cincinnatian edrioasteroid beds were mainly associated with shell pavements of Rafinesquina Hall and Clarke, 1892 brachiopods or Ambonychia Hall, 1847 bivalves rather than true hardgrounds (Meyer, 1990; Dattilo, 1998). Such pavements may have been stabilized by early cementation (Rassman, 1981) but in no cases were edrioasteroids found directly encrusting limestone surfaces. LOCALITY AND STRATIGRAPHY
Recently, a heavily encrusted hardground horizon, encrusted by four species of edrioasteroids (Echinodermata) and several species of large encrusting bryozoans, was discovered in the rubbly limestones of the Bellevue Member of the Grant Lake Formation in a set of roadcuts along State Rt. 3071 near Maysville, Mason County, Kentucky (Fig. 1). Subsequent search showed that the same hardground occurred in several nearby outcrops within 2 km of the original discovery site. It has not been traced further, although type locality of Carneyella ulrichi is in a railroad cut near Maysville (Bassler and Shideler, in Bassler, 1936) suggests that the surface may be exposed there as well. The Maysville hardground horizon occurs approximately seven meters above the base of the Bellevue Formation (Sumrall et al., 2001). It is exposed on the second highest bench in the road cut at the top of a series of beds between 10 and 25 cm in thickness that range from clay-rich, rubbly skeletal packstones to grainstones interbedded with thinner, more compact beds of grainstones and packstones. Most of these beds have sharp bases and sharp, irregular tops. A number of bed tops exhibit features such as sharp, irregular relief, staining, borings and/or encrusting organisms, indicative of firmground or hardground development. According to the stratigraphic definitions used by Schumacher (1992, 1998) these beds are assigned to the lower Bellevue Member of the Grant Lake Formation. They abruptly overlie a series of shales and thin to medium bedded limestones typically referred to the upper Fairview, but possibly correlative with the Miamitown Shale of Ohio. The Bellevue contact, in turn, occurs about 10 m above the base of an interval of distinctive ball and pillow deformation (seismites) in the upper Fairview Formation (Schumacher, 1992). The hardground interval falls within the middle of the Maysvillian Stage of the Cincinnatian Series, estimated to be about 440 Ma. This region lay about 0–25u south of the paleoequator (Schumacher, 1998). Some 10.3 square meters of the hardground surface were excavated and collected for laboratory preparation during the fall and winter of 1998–1999 (Fig. 1). Recovered slabs were oriented, cleaned and reassembled so that the surface spatial relationships of the hard substrate fauna could be studied. All edrioasteroid specimens were identified, located on the surface, and measured. The surface was also mapped to determine distribution patterns of the edrioasteroids and other fossils of this ‘‘terminal community.’’ These observations provide significant insights into the nature and distribution of an Upper Ordovician hard substrate community. HARDGROUND CHARACTERISTICS AND FAUNA
The Maysville hardground is developed on the upper surface of a brachiopod-rich packstone bed that ranges from at least two to ten centimeters in thickness and pinches out completely in one area. The limestone contains abundant,
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large valves of Platystrophia ponderosa Foerste, 1909, in varied stages of preservation from complete and unaltered to heavily corroded and bored remnants. Most of the hardground surface itself shows relatively minor relief although a small scarp about 2 cm high is present along the edge of the excavated slab. The entire surface is irregular on a centimeter high scale with lots of irregular anastomosing raised areas suggestive of interference ripples. Edrioasteroids and other encrusting fossils occur on a small fraction (less than 1 percent) of the total surface area and yet are clustered primarily into vaguely elongate north-south oriented patches along the surface (Fig. 1). Bryozoans on the surface are generally encrusting forms that in some areas form lips where they apparently overgrew mud on the surface of the hardground. Some surface areas are riddled with by Trypanites type borings. These borings are generally associated with areas colonized by bryozoans and typically penetrate the bryozoan and extend through the hardground bed. The Maysville hardground was overlain in places by yellowish-weathering calcisiltite up to 5 mm thick. This material locally buried edrioasteroids and other members of the terminal community. Edgewise brachiopods valves also occur in this matrix, indicating stirring of coarser sediments in the final burial event. This calcisilt is overlain by 2–5 cm of clay shale. Some portions of this shale have proven to be more or less barren, while other shale samples yielded abundant brachiopod valves and a phosphatic microfauna (mainly steinkerns of tiny gastropods and conodonts) and an exceptionally rich assemblage of scolecodonts including 52 form taxa (R. Fuchs, personal commun., 2001). This mudstone layer shows indistinct burrows, which in a few instances penetrated down to and disrupted plates of buried edrioasteroids and in other cases encircled them (Sumrall et al., 2001). The hardground fauna is dominated by about three species of trepostome bryozoans. The bryozoan colonies are large (1 to 40 cm across) irregular mounds, some of which have flatsided carinae (keels) that may project several centimeters above the hardground surface. Other faunal elements include: brachiopods (Hebertella occidentalis (Hall, 1847), Platystrophia ponderosa Petrocrania scabiosa (Hall, 1868)), cyclostome bryozoans, annelid worms, crinoids (Cincinnaticrinus sp.), and edrioasteroids Carneyella ulrichi, Carneyella pilea, Curvitriordo stecki n. sp., and Streptaster vorticellatus. The four species of edrioasteroids, although locally abundant (25.0 individuals per square meter), comprise a unique community dominated by rare forms, both in terms of species composition and specimen size. Large and small edrioasteroids are attached to the hardground and less commonly to bryozoan colonies. Several juvenile edrioasteroids, however, are attached to brachiopods in life position. In one place, a cryptic fauna occurs beneath an overhang formed by the binding of skeletal debris by a large encrusting bryozoan, with an edrioasteroid, bryozoan, and Petrocrania all growing into the cavity (Sumrall et al., 2001). The abundance of phosphatized fossil steinkerns, conodonts, and chitinous scolecodonts in some samples of shale directly adherent to the hardground suggests that the surface was partially overlain by a thin, condensed lag deposit. This geochemically resistant skeletal debris gradually accumulated on the hardground surface. Barren shale samples, also recovered from the site, may represent rapidly deposited obrutionary muds. Emplacement of the final mud layer was obviously rapid. Fragile imbricated skeletons of edrioasteroids clearly could
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only be preserved if they were buried very rapidly after death or were buried alive by sediment (Brett et al., 1997). It is surmised that the final depositional pulse probably came in the form of a suspended flow of mud or mud tempestite. It is clear that the burial mud blanket was not particularly thick, probably not more than about ten centimeters uncompacted (Sumrall et al., 2001). Post burial burrowing organisms were able to penetrate downward to the hardground and slightly disrupt the some of the entombed carcasses or pass around the perimeter of others. SIZE FREQUENCY DISTRIBUTION
Obrution surfaces, as represented by the edrioasteroid accumulation on the Maysville hardground, census living population that provide insight into the ecology of living assemblages. Because these occurrences are life assemblages, they fundamentally represent a different phenomenon than mortality studies of size frequency i.e., Richards and Bamback (1975). Time averaged accumulations represent cumulative size frequency distributions of numerous distinct cohorts, whereas obrution surfaces preserve single living communities providing appropriate data for inferring population dynamics (Cummins et al., 1986). In the case of the Maysville hardground, specimen diameter, a proxy for age, represents not the life expectancy of individuals of the species but the age structure of the population at the time of smothering and death. Three of the four species represented on the Maysville hardground are present in sufficient numbers to discuss size frequency. The exception is Carneyella pilea (Hall) of which there are two specimens with a mean diameter of 20.9 mm (Fig. 2.4). The remaining species showed fundamentally different size frequency distributions as noted in other polytaxic edrioasteroid populations (Sumrall, 2001; Sumrall et al., 2006). On the Maysville hardground, 121 specimens of Curvitriordo stecki n. sp. were located of which 116 could be measured for diameter. The size frequency shows a bimodal distribution with diameter means of 13.8 mm for the smaller specimens and 29.5 mm for the larger specimens, with a total mean of 16.4 mm standard deviation of 7.35, and skewness of 0.37. There is a 4.9 mm gap between the nodes and both of the modes are left skewed (Fig. 2.1). On the hardground, 125 specimens of Carneyella ulrichi Bassler and Shideler were identified of which 108 could be measured for diameter. The size frequency distribution is strongly left skewed with a skewness of 21.16, a mean diameter of 20.5 mm, and a standard deviation of 5.87 mm (Fig. 2.2). Only nine specimens of Streptaster vorticellatus (Hall) were identified on the Maysville hardground. All nine specimens could be measured for diameter with a mean of 21.3 mm, standard deviation of 1.72 mm and skewness of 0.98 (Fig. 2.3). The small number of specimens of this species suggests caution in interpreting these data. Left skewed populations as seen in Carneyella ulrichi suggest that either once established, the mortality rate among juvenile individuals is low resulting in a great number reaching maturity (likely), or that growth rate greatly slows with maturity resulting in an accumulation of large individuals through time. For Curvitriordo stecki, the bimodal distribution is clear (Fig. 2.1). This strongly suggests a period of hiatus in recruitment (seasonal breeding?) or some other factor that for a period of time resulted in little or no recruitment of new larvae. Interestingly, the mode of smaller specimens is similar in shape to the total population of C. ulrichi suggesting similar low mortality of established juveniles. This is in sharp contrast
FIGURE 2—Histograms showing the size frequency distribution of edrioasteroids on the Maysville hardground. 1, Curvitriordo stecki n. sp. showing a bimodal distribution (Note the absence of specimens with diameters between 21 and 25 mm); 2, Carneyella ulrichi Bassler and Shideler showing a left skewed distribution; 3, Streptaster vorticellatus (Hall) showing a tight unimodal distribution; 4, Carneyella pilea (Hall) showing two mature specimens.
with the weakly bimodal distribution observed for the Mississippian edrioasteroid Neoisorophusella lanei Kammer, Tissue, and Wilson, 1987 that showed a strongly right skewed population structure suggesting high juvenile mortality (Kammer et al, 1987). The tight mode of large individuals of Streptaster vorticellatus with a complete absence of smaller individuals (Fig. 2.3) suggests they matured from a single spat fall as was suggested for a similar distribution of Torquerisediscus kypsi Sumrall (Sumrall, 2001). SYSTEMATIC PALEONTOLOGY
Discussion.—Inclusion of Linnaean ranks reflects editorial policy rather than the views of the authors.
SUMRALL—ORDOVICIAN EDRIOASTEROIDS
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FIGURE 3—Uncommon edrioasteroid species on the Maysville hardground, all photographs whitened, 32.5 unless otherwise noted. 1, 3–4, Carneyella pilea (Hall): 1, oral area of CMCIP 53371-MV149-8a, 35 (Compare to figure 4.2); 3, slightly disrupted specimen CMCIP 53371-MV149-11; 4, well preserved specimen CMCIP 53371-MV149-8a (Note the lack of nodes on the surface of the specimen); 2, 5–7, Streptaster vorticellatus (Hall): 2, well preserved but slightly disrupted specimen CMCIP 53371-MV107-2; 5, very well preserved specimen CMCIP 53371-MV147-2 (Note that the interambulacra are covered with hard matrix and have not been prepared out); 6, 7, specimen CMCIP 53371-MV105-3: 6, whole specimen showing well preserved ambulacra; 7, detail of ambulacrum D showing extremely small interambulacral plates, large ‘‘cover plates’’ here interpreted as hood plates, bearing distal ‘‘conical spines’’ here interpreted as cover plates, 35 (Note that image is rotated relative to figure 6).
Class EDRIOASTEROIDEA Billings, 1858 Order ISOROPHIDA Bell, 1976a Suborder LEBETODISCINA Bell, 1976a Family LEBETODISCIDAE Bell, 1976a Genus STREPTASTER Hall, 1872 STREPTASTER VORTICELLATUS (Hall), 1866 Figure 3.2, 3.5–3.7 See synonymy in Bell, 1976a Streptaster vorticellatus (Hall), Sumrall et al., 2001, Fig. 3.3. Discussion.—The nine specimens of Streptaster vorticellatus (Hall) found on the Maysville hardground are all large and well preserved. Streptaster Hall is an unusual edrioasteroid in the construction of the ambulacra that are unlike most other edrioasteroids assigned to Lebetodiscidae. The ambulacra are formed from three plate layers as recently described for
pyrgocystitids (Sumrall, 2007; Sumrall and Zamora, in press). Floor plates are small and proximally imbricating. These are overlain by what Bell (1976a) termed columnar cover plates that each bear a conical movable spine (Fig. 3.5, 3.7). The position of these spines atop the cover plates in incongruous with the condition seen in any other edrioasteroid bearing secondary cover plates. Furthermore the way that the cover plates articulate with the floor plates is unlike any other lebetodiscinid – atop the floor plate rather than lying across the top with lateral extensions. Here these plates are interpreted differently. The floor plates are floor plates, the cover plates are hood plates (sensu Guensburg and Sprinkle, 1994) and the spines are vestibule cover plates lying atop the hood plates. Material.—Figured specimens for this study of Streptaster vorticellatus (Hall), include: CMCIP 53371-MV105-3; CMCIP
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53371-MV107-2; CMCIP 53371-MV147-2. Additional specimens stored in the collections of Cincinnati Museum Center under the number CMCIP 53371. Occurrence.—Specimens of Streptaster vorticellatus (Hall) described here were collected from the Bellevue Member of the Grant Lake Formation in a set of roadcuts along State Rt. 3071 near Maysville, Mason County, Kentucky. Family CARNEYELLIDAE Bell, 1976a Genus CARNEYELLA Foerste, 1917 Discussion.—Interestingly, all specimens of Carneyella regardless of species show identical plating of the ambulacral cover plate system. Three greatly enlarged primary oral plates form the central portion of the peristomial cover and all specimens lack cover plates on the short shared ambulacra. All of the ambulacra have a simple biseries of cover plates covering the ambulacral tunnel, but unlike has been noted in other echinoderms these cover plates do not follow an insertion pattern consistent with Love´n’s Law. Plating that follows Love´n’s Law will have identical plating on the A C and E ambulacra while different plating pattern is used for the B and D ambulacra. This results in a symmetrical arrangement of plating around the peristome as shown (Hotchkiss, 1998; Sumrall and Wray, 2007). For Carneyella, the opposite pattern is expressed. The A, B, and D ambulacra all begin with plates on the left side if viewed proximally to distally (Fig. 4). The C and E ambulacra have the first plate on the right. Interestingly, this reversed plating pattern is unrelated to the right left asymmetry of the body openings and therefore does not represent reversed larval development as has been shown for aberrant individual edrioasteroids (Smith and Arbizu, 1987; Sumrall, 2001). Instead it may simply reflect a developmental constraint in plate insertion as shown for glyptocystitoid rhombiferans (Sumrall, 2008). In this example, Love´n’s Law resulted from the point of insertion of oral plated early in development. This resulted in the left brachioles of the shared ambulacra being placed in line with the brachioles of the B and D ambulacra. This was manifest at maturity as all ambulacra bearing the first brachiole facet on the left except for B and D which had the first two on the left. In Carneyella we see a similar constraint simply bearing the opposite result. The first cover plate on the right side of the C ambulacrum may be related to the enlargement of the first right cover plate and its association with the hydropore opening (Fig. 4). For the E ambulacrum it seems related with the anterior shift of the left LBP. CARNEYELLA ULRICHI Bassler and Shideler, 1936 Figures 4.1, 5 See synonymy in Bell, 1976a Carneyella ulrichi Bassler and Shideler, Sumrall et al., 2001, Fig. 3.1, 3.8, 3.9. Amended diagnosis.—Carneyella with large pustules on external surface of plates; most cover plates bearing single pustule along abradial margin forming rows parallel to ambulaca. Description.—Large Carneyella with domal, circular theca bounded by peripheral rim theca covered with large organized pustules, and interambulacra divided by five curved ambulacra (Fig. 5). Oral area centered at junction of ambulacral system, dominated by three very large primary oral plates; largest primary oral plate centered in CD interambulacral area, roughly triangular in outline with point directed posteriorly, anterior margin slightly chevron-shaped indented along midline where posterior plate articulated to paired
FIGURE 4—Plating of the oral areas of species of Carneyella Foerste. 1, Camera lucida drawing of the oral area of showing Carneyella ulrichi Bassler and Shideler CMCIP 53371-MV135-6 showing the plating and distribution of nodes and plates, 320 (Note that the first cover plates on the distal ambulacra are on the left except for C and E where they are on the right. Nearly all of the cover plates have a single node near the abradial edge of the exposed portion of the cover plate, but several plates lack nodes and one on ambulacrum A has two); 2, Camera lucida drawing of the oral area of showing Carneyella pilea (Hall) CMCIP 53371-MV1498a showing the plate distribution, 325. Note that the first cover plates on the distal ambulacra are on the left except for C and E where they are on the right. A–E are the ambulacral designations; HO 5 hydropore oral; LBP 5 lateral bifurcation plates; PO 5 Primary oral plates; R 5 first right cover plate of the C and E ambulacra.
anterior primary oral cover plates; ornamented typically with three large pustules along posterior left margin, but variation is noted (Figs. 4.1, 5.3, 5.15), smaller accessory pustules may be present along midline with maturity, high sharp ridge present along suture with other primary oral plates (POP); two smaller POPP positioned in AE and AB interradii; wide-lathe shaped, articulated with lateral bifurcation plates (LBP) without intervening anterior shared cover plates, each with large node near distal edge of plate addition of smaller more proximal node with maturity, contact edges adjacent to other PPOP with high sharp edge; all POPP with wide, well
SUMRALL—ORDOVICIAN EDRIOASTEROIDS developed intrathecal extensions; LBPP relatively small, form the branching points of the shared ambulacra; right and left LBPP offset to anterior (Figs. 4.1, 5.3). Hydropore located in proximal right CD interambulacrum, formed from enlarged first right cover plate of C ambulacrum, and elongate hydropore oral; hydropore oral in contact with first two to three right cover plates of C ambulacrum (Fig. 4.1). Ambulacra branch from peristome in 2-1-2 pattern; A, B and D ambulacra plates with biserial cover plates starting on the left is viewed proximal to distal; C and E cover plates start on right (Fig. 4.1); first right cover plate on ambulacrum C greatly enlarged and associated with hydropore oral; first left cover plate on D ambulacrum somewhat enlarged; ambulacra all curved all counter clockwise except C clockwise (Fig. 5.5). Ambulacra curve evenly throughout length to peripheral rim, terminate bluntly just beyond adjacent interambulacrum; cover plates narrow, lathe-shaped, biserial with extensive intrathecal extensions (Fig. 5.14), with strong ornament, single large node along the abradial edge of exposed position of cover plate, adradial tip with elongate ridge; intrathecal extensions, long extending nearly as far as exposed portion of plate, narrow and tapering with blunt terminus forming distinct gap between adjacent plates (Fig. 5.14); intrambulacral extensions large, scroll-shaped, extending anteriorly beyond edge of exterior portion of plate (Fig. 5.11); cover plate width on interior of curved ambulacrum much narrower than exterior width. Interambulacra relatively large, CD largest and BC smallest because of curvature of C ambulacrum; interambulacral plates relatively small, numerous, imbricate in juveniles, becoming nearly adjacent with maturity; each plate with two to ten nodes depending on plate size (Fig. 5.16) nodes evenly distributed across interambulacral areas. Periproct indistinct because of ornament, plates with irregular low conical array of lathe-shaped plates each bearing one or two large nodes. Peripheral rim very wide, plated with eight or nine irregular circlets of highly imbricate plates; most proximal circlets not differentiated from other circlets; proximal circlets with large, transversely elongate, plates becoming much smaller and radially elongate distally; bottom surface of peripheral rim unknown; bottom surface of theca unplated. Discussion.—Carneyella ulrichi Bassler and Shideler was previously known from a single specimen USNM S-3964 housed in the U. S. National Museum. This specimen was collected from a nearly railroad cut in approximately the same stratigraphic position. It is comparable in size to the ones described here and attached to a brachiopod. The specimen has been taphonomically slumped toward the D ambulacrum, but is otherwise in good condition. Stratigraphically, this specimen is comparable to the Maysville slab and shows all of the diagnostic features common to the larger collection described here. Carneyella ulrichi clearly differs from C. pilea (Hall) by the presence of large nodes covering the theca. It differs from C. faberi (Miller) by the much larger nodes and the restriction of nodes to one per cover plate in nearly every case. The distribution of nodes on the interambulacral plates and the peripheral rim is dispersed and variable between specimens. The distribution on the cover plate series is, however, more controlled. In general, there is a single large node at the abradial edge of the exposed portion of each cover plate. In some individuals these nodes are poorly expressed in some ambulacra (i.e., a ambulacrum of Fig. 5.10). Also, in rare cases, the proximal-most cover plates may have a second node as reported by Bell (1976a) (Fig. 5.18). This may be a maturity
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factor. The expression of nodes on the primary orals is also fairly consistent between specimens. Nodes are medially plated on the anterior oral plates and along the left margin of the posterior plate though there is some variation (Figs. 4.1, 5.15). Ontogeny.—Little ontogenetic information is available for species on the Maysville hardground. Although a number of very small specimens are present, their poor preservation precludes their use in ontogenetic analyses. For Carneyella ulrichi, ontogeny proceeds in manner detailed by Bell (1976b) with small juveniles having straight ambulacra (Fig. 3.1) that gradually become more curved throughout ontogeny (Fig. 5.2, 5.12, 5.16). Nodes are present on all of the plates early in ontogeny (Fig. 5.1) and become more pronounced with maturity (Fig. 5.16). Also noted is a general tendency for the number of nodes to increase with age on the primary oral plates, though there is much variation in the expression of this characteristic. Material.—Figured specimens for this study of Carneyella ulrichi Bassler and Shideler, include: CMCIP 53371-MV10210; CMCIP 53371-MV107-5; CMCIP 53371-MV112-1, 2, 3; CMCIP 53371-MV125-6; CMCIP 53371-MV135-1, 4, 5, 6, 15; CMCIP 53371-MV149-12, 13, 15. Additional specimens stored in the collections of Cincinnati Museum Center under the number CMCIP 53371. Occurrence.—Specimens of Carneyella ulrichi Bassler and Shideler described here were collected from the Bellevue Member of the Grant Lake Formation in a set of roadcuts along State Rt. 3071 near Maysville, Mason County, Kentucky. CARNEYELLA PILEA (Hall), 1866 Figures 3.1, 3.3–3.4; 4.2 See synonymy in Bell, 1976a Carneyella pilea Bassler and Shideler, Sumrall et al., 2001, Fig. 3.5. Discussion.—Carneyella pilea (Hall) is represented in the Maysville hardground by two large specimens (Fig. 3.3–3.4). These individuals are easily distinguishable from the locally more common Carneyella ulrichi Bassler and Shideler because they lack all hint of the large nodes that characterize C. ulrichi having instead fine rugose surface ornamentation consistent with the species assignment (Fig. 3.1). The width of the peripheral rim is also somewhat narrower. These specimens add no new information concerning the morphology of the species. Material.—Figured material from the Maysville hardground includes CMCIP 53371-MV149-8a and CMCIP 53371-MV149-11. Occurrence.—Specimens of Carneyella pilea (Hall) described here were collected from the Bellevue Member of the Grant Lake Formation in a set of roadcuts along State Rt. 3071 near Maysville, Mason County, Kentucky. Suborder ISOROPHINA Bell, 1976a Family ISOROPHIDAE Bell, 1976a Genus CURVITRIORDO Bell, 1976a Amended diagnosis.—Isorophid with narrow ambulacra strongly curving counter clockwise except C curving clockwise; ambulacral cover plates with tertiary plates between secondary plates. Discussion.—Curvitriordo Bell is a poorly known and understood edrioasteroid genus. It was erected to accept Isorophus kentuckyensis Bassler and Isorophus shideleri Bassler. These species are based on three poorly preserved specimens that are all very large, but also bear tertiary cover
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FIGURE 5—Photographs of Carneyella ulrichi Bassler and Shideler, all images whitened, 32.5 unless otherwise noted. 1, Juvenile specimen CMCIP 53371-MV125-6 showing short straight ambulacra and poorly developed pustules, 35; 2, CMCIP 53371-MV112-2; 3, detail of oral area of CMCIP 53371-MV149-15 showing three primary oral plates nearing pustules and a lack of cover plates on the shared ambulacra, 35; 4, CMCIP 53371-MV1075; 5, CMCIP 53371-MV135-6 showing somewhat gaped B ambulacral cover plates, compare to Fig. 11; 6, CMCIP 53371-MV135-7; 7, CMCIP 53371MV149-15; 8, CMCIP 53371-MV102-10 showing a slightly disrupted theca; 9, CMCIP 53371-MV135-4; 10, CMCIP 53371-MV149-13; 11, detail of B ambulacrum of CMCIP 53371-MV135-6 showing proximally directed scroll-shaped intrambulacral extensions, 37.7; 12, CMCIP 53371-MV135-15; 13,
SUMRALL—ORDOVICIAN EDRIOASTEROIDS plates in the proximal ambulacra and the long, tapering distal ambulacra (Bell, 1976a). Curvitriordo shideleri is too poorly preserved to be diagnosable, missing the oral area and most of the ambulacral plating. This species is here restricted to the holotype pending the discovery of more complete material. The genus is very similar to Isorophus Foerste. Interestingly, specimens of C. kentuckyensis and C. stecki n. sp. are all deep maroon in color whereas, at least on the Maysville hardground, other species are light gray in color. It is unknown the significance of this observation, but similar color differences by species have been noted for crinoids from Legrand, Iowa (Ausich, 1999). CURVITRIORDO STECKI n. sp. Figures 6, 7 Curvitriordo n. sp., Sumrall et al., 2001, Fig. 3.2. Diagnosis.—Large Curvitriordo with long curved slender ambulacra tapering distally, cover plates in well-developed triple biseries proximally; lateral bifurcation plates long and narrow anterior primary oral plates poorly differentiated. Description.—Large Curvitriordo with domal, circular theca bounded by peripheral rim interambulacra divided by five curved ambulacra with extremely small BC interambulacrum (Fig. 6.14). Oral area centered on oral surface covered by complex pattern of primary oral plates (POP), lateral bifurcation plates (LBP), and shared cover plates (Fig. 7.2); anterior POPP slightly differentiated, form bifurcation of shared ambulacra and A ambulacrum, separated from LBPP by one primary shared cover plate and associated secondary and tertiary cover plates; posterior POPP undifferentiated; posterior shared cover plates with complex triple biserial pattern; LBPP long and narrow; hydropore oral elongate, lying along proximal edge of foreshortened right shared cover plates and foreshortened proximal most right cover plates of C ambulacrum (Fig. 7.2). Ambulacra arranged into 2-1-2 pattern all strongly curved with A, B, D, and E curving counter clockwise and C clockwise, curved throughout length with slight taper distally and blunt termination; ambulacral tips at maturity with considerable overlap with adjacent ambulacrum; C ambulacrum relatively shorter, with strong proximal flexure at distal tip terminating just posterior of periproct; distal tip of D ambulacrum with slight distal flexure where terminated just past end of C ambulacrum (Fig. 6.10, 6.14); one abnormal specimen with strongly counterclockwise curved C ambulacrum similar to other ambulacra (Fig. 6.8). Cover plates arranged into complex triple biseries (Figs. 6.11, 7.1); primary cover plates alternate with secondary cover plates interfingered with tertiary cover plates; plates arranged such that each plate type is in contact with its counterpart across perradial suture; cover plates lacking well developed intrathecal extensions; instead cover plates extend just beyond hinge with underlying floor plates and wedge shaped with extreme abradial thickness; intrambulacral extensions suggestive. Floor plates small shallow, uniserial with slight hint of imbricate suture, lacking accessory processes; hinge-notch and spur present along upper limbs of floor plate. Interambulacra plated with numerous small imbricate, semipolygonal inter-
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ambulacral plates that become less imbricate ontogenetically (Fig. 6.14); interambulacral plates smooth in adults, but ornament with fine pits in juvenile specimens. Anal pyramid relatively large, conical, valvular anal structure type, bearing approximately ten lathe-shaped plates, bordered by ring of smaller interambulacral plates (Fig. 6.10). Pedunculate zone poorly developed, bearing approximately 3 unorganized, but highly imbricate circlets of plates at maturity, positioned between ambulacral and peripheral rim. Peripheral rim well developed with approximately six rows of highly imbricate plates; proximal circlet strongly differentiated bearing highly transversely elongate plates (Fig. 6.14); remaining circlets with progressively smaller plates, but all equant in outline. Bottom surface of peripheral rim unknown, bottom surface of theca unplated. Discussion.—Curvitriordo stecki n. sp. shows an unusual transformation in surface ornamentation ontogenetically. Juveniles have a the surfaces of the interambulacral plates and peripheral rim covered with fine pits that diminish with maturity. It differs from C. kentuckyensis by bearing smaller and more numerous plates in the shared ambulacra. It is not clear how C. stecki differs from C. shideleri because the diagnostic points of the later are not preserved in the unique holotype. Etymology.—Named in honor of C. Steck, then of The Ohio State University, who found the first specimens of the Maysville Hardground. Types.—The holotype of Curvitriordo stecki n. sp. is CMCIP 53371-MV125-4. Paratypes include CMCIP 53371-MV1002; CMCIP 53371-MV102-2, 3, 4; CMCIP 53371-MV105-2; CMCIP 53371-MV107-1, 4, 8; CMCIP 53371-MV125-5; CMCIP 53371-MV135-11b; CMCIP 53371-MV149-14. Additional specimens stored in the collections of Cincinnati Museum center under the number CMCIP 53371. Ontogeny.—Little ontogenetic information is available for species on the Maysville hardground. Although a number of very small specimens are present, their poor preservation precludes their use in ontogenetic analyses. The ontogeny of Curvitriordo stecki is poorly constrained. Very small specimens have straight ambulacra that become increasingly curved ontogenetically (Fig. 6.6, 6.7, 6.14). With maturity there is a tendency to develop a large number of peduncular plates between the ambulacra and the peripheral rim allowing greater extendibility of the theca (Sumrall, 1993) (Fig. 6.10, 6.14). There is also a change in surface ornamentation of the interambulacral plates. Specimens that have a diameter of less than about 15 mm have a finely pitted surface to the interambulacral plates and peripheral rim that fades with age. Finally, smaller specimens do not express the tertiary cover plates in the ambulacra. These plates are expressed in greater prominence with maturity from a diameter of about 10 mm on. Abnormalities.—One specimen shows an inverted C ambulacrum that curves counterclockwise rather than the typical clockwise direction (Fig. 6.8). the fact that this specimen achieved great size (thecal diameter of 30 mm) suggests that it did not affect the edrioasteroid in any serious way. Similar anomalies have been reported for other edrioasteroids, though
r CMCIP 53371-MV112-1 showing the plating of the peripheral rim and the distribution of pustules; 14, detail of the C ambulacrum of disrupted specimen CMCIP 53371-MV102-10 showing complete cover plates (Note that the node projects at an angle with respect to the cover plate, and the extremely long and narrow intrathecal extensions of the cover plates, 35); 15, detail of the oral area of CMCIP 53371-MV135-5 showing the three prominent oral cover plates, hydropore oral and distribution of nodes in the oral area, 35; 16, CMCIP 53371-MV112-3 showing well preserved theca; 17, CMCIP 53371MV149-12; 18, CMCIP 53371-MV135-5 showing well preserved theca.
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FIGURE 6—Photographs of Curvitriordo stecki n. sp. All specimens whitened, 32.5 unless otherwise noted. 1, extremely large and somewhat disrupted paratype CMCIP 53371-MV107-1 (Note the trace fossil passing through the oral surface); 2, paratype CMCIP 53371-MV149-14; 3, paratype CMCIP 53371-MV102-3; 4, paratype CMCIP 53371-MV105-2 showing a well-preserved theca with curved ambulacra; 5, paratype CMCIP 53371-MV135-11b; 6, small paratype CMCIP 53371-MV102-2 showing slightly curved ambulacra; 7, well preserved but naturally etched paratype CMCIP 53371-MV102-4 showing complex cover plate patterns on the ambulacral system; 8, very large paratype CMCIP 53371-MV107-4 (Note that the C ambulacrum curves counterclockwise instead of the usual clockwise direction but the specimen is otherwise normal); 9, paratype CMCIP 53371-MV107-8 showing the
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specimen from the hardground. Access to collections was provided by B. Hanke, Cincinnati Museum Center. Two reviewers, T. Kammer and A. B. Smith, provided valuable edits to this manuscript. This research was supported in part by NSF grant EAR-0745918. REFFERENCES
FIGURE 7—Camera lucida drawing of the proximal cover plates and oral area of Curvitriordo stecki n. sp. holotype CMCIP 53371-MV125-4. 1, cover plates of the proximal E ambulacrum, 325 (Note that the cover plates are arranged into primary, secondary and tertiary series. Incompleteness of the tertiary series results from slight plate shifting post mortem and weathering); 2, oral area showing long and narrow primary oral plates (PO) and lateral bifurcations plates (LBP), 39.5. There is foreshortening of the proximal right cover plates along the hydropore oral (HO). Several areas are missing or uninterpretable because of post mortem plate shifting and weathering. A–E are the ambulacral designations.
the phenomenon is rather uncommon (Bell, 1976a; Sumrall et al., 2006). This is different from complete larval inversion as has been reported (Smith and Arbizu, 1987; Sumrall, 2001) Occurrence.—Specimens of Curvitriordo stecki n. sp. described here were collected from the Bellevue Member of the Grant Lake Formation in a set of roadcuts along State Rt. 3071 near Maysville, Mason County, Kentucky. ACKNOWLEDGMENTS
This project was made possible through hard work of many people who helped excavate the Maysville hardground including P. T. Work and D. M. Work, Maine State Museum, C. E. Brett and D. M. Meyer, of the University of Cincinnati, F. J. Gahn, BYU, Idaho, S. Cornell, Shippensburg University, T. Bantell, D. Cooper, S. Felton, and R. Fuchs of the Dry Dredgers. Special thanks to C. Steck who discovered the first
AUSICH, W. I. 1999. Lower Mississippian Hampton Formation at LeGrand, Iowa, USA, p. 135–138. In H. Hess, W. I. Ausich, C. E. Brett and M. J. Simms (eds.), Fossil Crinoids. Cambridge University Press, Cambridge. BASSLER, R. S. 1936. New species of American Edrioasteroidea. Smithsonian Miscellaneous Collections, 95:1–33. BELL, B. M. 1976a. A Study of North American Edrioasteroidea. New York State Museum Memoir 21, 446 p. BELL, B. M. 1976b. Phylogenetic implications of ontogenetic development in the class Edrioasteroidea (Echinodermata). Journal of Paleontology, 50:1001–1019. BILLINGS, E. 1858. On the Asteriadae of the Lower Silurian rocks of Canada. Geological Survey of Canada, figures and descriptions of Canadian organic remains. Decade, 3:75–85. BRETT, C. E., H. A. MOFFAT, AND W. L. TAYLOR. 1997. Echinoderm taphonomy, taphofacies, and lagersta¨tten, p. 147–190. In J. A. Waters and C. G. Maples (eds.), Geobiology of Echinoderms, Paleontological Society Papers, 3. Paleontological Society, Pittsburgh. CUMMINS, H., E. N. POWELL, R. J. STANTON, AND G. STAFF. 1986. The size frequency distribution in palaeontology: Effects of taphonomic processes during formation of molluscan death assemblages in Texas bays. Palaeontology, 29:495–518. DATTILO, B. F. 1998. The Miamitown Shale; stratigraphic and historic context (Upper Ordovician, Cincinnati, Ohio, region), p. 49–59. In R. A. Davis and R. J. Cuffey (eds.), Sampling the layer cake that isn’t: The stratigraphy and paleontology of the type-Cincinnatian. Edited by State of Ohio, Department of Natural Resources, Division of Geological Survey, Columbus, Ohio. DATTILO, B. F., D. L. MEYER, K. DEWING, AND M. R. GAYNOR. 2009. Escape traces associated with Rafinesquina alternata, an Upper Ordovician strophomenid brachiopod from the Cincinnati Arch Region. Palaios, 24:578–590. FOERSTE, A. F. 1909. Preliminary notes on Cincinnatian and Lexington fossils. Denison University Science Laboratories Bulletin, 14:289–334. GOAD, L., D. HALL, J. CULVER, B. DAVIS, D. SMITH, C. D. SUMRALL, AND T. A. DEXTER. 2006. Criteria for determining live vs. dead faunal elements and faunal interactions on an obrution surface from the upper Ordovician Miamitown Shale, Sharonville, Ohio. Geological Society of America, Abstracts with Program, 39:24–8. HALL, J. 1847. Natural History of New York, Paleontology of New York, 1. C. Van Benthuysen, Albany, 388 p. HALL, J. 1866. Descriptions of some new species of Crinoidea and other fossils. New York State Museum of Natural History Annual Report, 20:1–17 HALL, J. 1872. Descriptions of new species of Crinoidea and other fossils from the strata of the age of the Hudson River Group and Trenton Limestone. New York State Museum of Natural History Annual Report, 24:205–224. HALL, J. 1868. Note on the genus Eichwaldia. Twentieth Annual Report of the Regents of the University of the State of New York, on the Condition of the State Cabinet of Natural History, p. 274–278. HALL, J. AND J. M. CLARKE. 1892. An introduction to the study of the genera of Paleozoic Brachiopoda, part 1. Palaeontology of New York, New York Geological Survey, 8: 367. HOTCHKISS, F. H. C. 1998. A ‘‘rays as appendages’’ model for the origin of pentamerism in echinoderms. Paleobiology, 24:200–214. KESLING, R. V. AND L. W. MINTZ. 1960. Internal structures in two edrioasteroid species, Isorophus cincinnatiensis (Roemer) and Carneyella pilea (Hall). University of Michigan Museum of Paleontology, Contribution, 15:315–348. MEYER, D. L. 1990. Population paleoecology and comparative taphonomy of two edrioasteroid (Echinodermata) pavements: Upper Ordovician of Kentucky and Ohio. Historical Biology, 4:155–178.
r sacrificial pit-like ornamentation common in small specimens; 10, well preserved paratype CMCIP 53371-MV125-5 showing excellent preservation except for a slight disruption of the peristome; 11, detail of the proximal D ambulacrum of holotype CMCIP 53371-MV125-4 showing the complex three tiers of cover plates, 37.5, compare to Figure 7.1; 12, detail of the oral area of paratype CMCIP 53371-MV100-2 showing the complexities of the cover plate pattern over the peristome, 35; 13, paratype CMCIP 53371-MV100-2 showing well preserved oral area despite being disrupted by burrowing; 14, holotype CMCIP 53371-MV125-4 showing a very well-preserved theca and ambulacral system. Note that the specimen is eroded on the peripheral rim between 11:00 and 12:00 and that the peripheral rim is disrupted between 1:00 and 3:00.
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MEYER, D. L. AND B. DATTILO. 2008. Living on the edge: Epizoan encrustation and alternative life orientations of the Upper Ordovician strophomenid brachiopod Rafinesquina from the Cincinnati Arch region. Geological Society of America Abstracts with Programs, 40:84. RASSMAN, B. 1981. A sedimentological comparison of two dissimilar Ordovician edrioasteroid pavements (hardgrounds). M. S. thesis, University of Cincinnati, Cincinnati. RICHARDS, R. P. AND R. K. BAMBACH. 1975. Population dynamics of some Paleozoic brachiopods and their paleoecological significance. Journal of Paleontology, 49:775–798. ROEMER, F. 1851. Beitra¨ge zur Kenntniss der fossilen Fauna des devonischen Gebirges am Rhein. Decheniana (Verhandlungen des Naturhistorischen Vereins Rheinlands und Westfalens), 8:357–376. ROBERTS, J., S. BRELLENTHIN, A. FULLER, C. STEWART, C. D. SUMRALL, AND T. A. DEXTER. 2006. Space utilization by faunal elements on a bivalve shell pavement, Upper Ordovician Miamitown Shale, Sharonville, Ohio. Geological Society of America, Abstracts with Program, 39:24–9. SCHUMACHER, G. A. 1998. A new look at the Cincinnatian series from a mapping perspective in R. A. Davis and R. J. Cuffey (eds.), Guidebook No. 13, Sampling the layer cake that isn’t: The stratigraphy and paleontology of the Type-Cincinnatian, (field trip for 1992 Annual Meeting of Geological Society of America). Ohio Division of Geological Survey. SCHUMACHER, G. A. 1992. Lithostratigraphy, clyclic sedimentation, and event stratigraphy of the Maysville, Kentucky, area, Stop 8, p. 165–172. In F. R. Ettensohn (ed.), Changing interpretations of Kentucky geology: Layer cake, facies, flexure, and eustasy (field trip for 1992 Annual Meeting of Geological Society of America). Ohio Division of Geological Survey Miscellaneous Report 5. SMITH, A. B. AND M. A. ARBIZU. 1987. Inverse development in a Devonian edrioasteroid from Spain and the phylogeny of the Agelacrinitidae. Lethaia, 20:49–62.
SUMRALL, C. D. 1993. Thecal designs in isorophinid edrioasteroids. Lethaia, 26:289–302. SUMRALL, C. D. 2001. Paleoecology of two new edrioasteroids from a Mississippian hardground in Kentucky. Journal of Paleontology, 75:136–146. SUMRALL, C. D. 2007. What is a pyrgocystid? New evidence from an Early Ordovician edrioasteroid fauna from Morocco. Geological Society of America, Abstracts with Program, 40:22–4. SUMRALL, C. D. 2008. The origin of Love´n’s Law in glyptocystitoid rhombiferans and its bearing on the plate homology and the heterochronic evolution of the hemicosmitid peristomal border, p. 228–241. In W. I. Ausich and G. D. Webster (eds.), Echinoderm Paleobiology. University of Indiana Press. SUMRALL, C. D. AND G. A. WRAY. 2007. Ontogeny in the fossil record: diversification of body plans and the evolution of ‘‘aberrant’’ symmetry in Paleozoic echinoderms. Paleobiology, 33(1):149–163. SUMRALL, C. D. AND S. ZAMORA. In press. Ordovician edrioasteroids from Morocco: Faunal exchanges across the Rheic Ocean. Journal of Systematic Palaeontology. SUMRALL, C. D., J. SPRINKLE, AND R. M. BONEM. 2006. An edrioasteroid-dominated echinoderm assemblage from a Lower Pennsylvanian marine conglomerate in Oklahoma. Journal of Paleontology, 80: 229–244. SUMRALL, C. D., C. E. BRETT, P. T. WORK, AND D. L. MEYER. 2001. Taphonomy and paleoecology of an edrioasteroid encrusted hardground in the lower Bellevue Formation at Maysville, Kentucky, p. 123–131. In T. J. Algeo and C. E. Brett (eds.), Sequence, Cycle & Event Stratigraphy of Upper Ordovician & Silurian Strata of the Cincinnati Arch Region. Field Trip Guidebook in conjunction with the 1999 Field Conference of the Great Lakes Section SEPM-SSG and the Kentucky Society of Professional Geologists, Guidebook 1, Series XII. Kentucky Geological Survey, Lexington.
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