— Royal Ontario Museum | [IFE SCIENCES 4~CONTRIBUTIONS — 146 Stipatocrinus, a New and Unusual Camerate Crinoid from the Lower Silurian of Western New York James D. Eckert and Carlton E. Brett ROYAL ONTARIO MUSEUM LIFE SCIENCES PUBLICATIONS INSTRUCTIONS TO AUTHORS Authors should prepare their manuscripts carefully accord- ing to the following instructions; failure to do so will result in the manuscript’s being returned to the author for revision. All manuscripts are considered on the under- standing that they are not currently offered for publication elsewhere. 1. General Papers for publication are accepted from ROM staff members and research associates, and from researchers reporting on work done with ROM collec- tions. Monographs on the flora and/or fauna of Ontario may be considered for publication by authors not affiliated with the ROM. Financial contributions to- wards publication will be welcome. 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Authors are reminded that when illustrations are reduced magnification factors will change, and that they are responsible for the conver- sion. For details, see Guide to Authors. LIFE SCIENCES CONTRIBUTIONS 146 Stipatocrinus, a New and Unusual Camerate Crinoid from the Lower Silurian of Western New York James D. Eckert and Carlton E. Brett ROM ROYAL ONTARIO MUSEUM ROYAL ONTARIO MUSEUM PUBLICATIONS IN LIFE SCIENCES The Royal Ontario Museum publishes three series in the Life Sciences: CONTRIBUTIONS: a numbered series of original scientific publications. OCCASIONAL PAPERS: a numbered series of original scientific publications, primarily short and of taxonomic significance. MISCELLANEOUS PUBLICATIONS: an unnumbered series on a variety of subjects. All manuscripts considered for publication are subject to the scrutiny and editorial policies of the Life Sciences Editorial Board, and to independent refereeing by two or more persons, other than Museum staff, who are authorities in the particular field involved. LIFE SCIENCES EDITORIAL BOARD Senior Editor: E. J. Crossman Editor: Judith L. Eger Editor: C. Darling External Editor: C. S. Churcher Manuscript Editor: Judith L. Eger Production Editor: Barbara Ibronyi James D. Eckert completed his M.Sc. studies in the Department of Geology at the University of Toronto in 1981. He is currently continuing graduate studies in the De- partment of Geological Sciences, University of Rochester, Rochester, New York. Carlton E. Brett is associate professor in the Department of Geological Sciences, Uni- versity of Rochester. Canadian Cataloguing in Publication Data Eckert, James D., 1952- Stipatocrinus, a new and unusual camerate crinoid from the Lower Silurian of western New York (Life sciences contributions ; 146) Bibliography: p. ISBN 0-88854-336-0 1. Crinoidea, Fossil. 2. Paleontology — New York (State) — Ordovician. 3. Paleontology — New York (State). I. Brett, Carlton Elliot. If. Royal Ontario Museum. III. Title. [V. Series. QE782.E24 1987 563'.91'097479 C87-094782-6 Publication Date: 15 November 1987 ISBN 0-88854-336-0 ISSN 0384-8159 © Royal Ontario Museum, 1987 100 Queen’s Park, Toronto, Canada, M5S 2C6 PRINTED AND BOUND IN CANADA AT THE ALGER PRESS Stipatocrinus, a New and Unusual Camerate Crinoid from the Lower Silurian of Western New York Abstract Stipatocrinus hulveri gen. et sp. nov. is described from the Upper Llandoverian Reynales Formation of western New York. Diagnostic characters of this unusual camerate crinoid include a peculiar cup in which the lowest circlet, consisting of two large and two small plates designated as basals divided by sutures passing through the AE-interray and C- ray, possesses a combination of infrabasal, basal, and radial features. Unique t-shaped radials bridge interrays consisting of numerous small interbrachials irregular in shape and arrangement. Stipatocrinus probably represents an archaic, previously unrecognized lin- eage of camerate crinoids that persisted into the Silurian but became extinct in the late Llandoverian. Thinly plated, flexible interrays of Stipatocrinus reduced metabolic cost of skeletal growth and possibly aided in respiration. Introduction Crinoids are poorly represented in Lower Silurian (Llan- doverian) strata of eastern North America. This interval is critical to understanding the evolution of the class, for it followed major Late Ordovician extinctions that deci- mated crinoids and other groups of marine invertebrates and preceded major taxonomic radiation and restructuring of crinoid assemblages in the Late Silurian (Wenlockian). One might predict, therefore, that Llandoverian crinoid assemblages would comprise transitional forms, including ancestral stocks of certain of the major Wenlockian clades. Indeed, such precursor taxa have been reported from the Hopkinton Dolomite (late Llandoverian, C,;—C,) in lowa (Witzke, Frest, and Strimple, 1979; Witzke and Strimple, 1981), and a slightly older fauna is known from the Brass- field Formation of Ohio (Ausich, 1985, 1986a, 1986b) in strata considered to be of late Llandoverian (C,—C,) age (Berry and Boucot, 1970). Potential ancestors of Wen- lockian crinoids also occur in the Cataract Group of On- tario (Eckert, 1984) and in the lower Clinton Group (middle to late Llandoverian, B,—-C,) of the northern Appalachian Basin in New York State (Eckert, in prep.). However, Early Silurian crinoid assemblages of Ontario and New York State are also distinctly Ordovician in aspect and characterized by persistence of primitive lineages. For ex- ample, Ptychocrinus medinensis, a species closely related to the Late Ordovician crinoid P. splendens, is locally abundant in the Power Glen Formation (early Llandover- ian, A,-A,) of New York and the Cabot Head Formation of Ontario (Brett, 1978; Eckert, 1984). The Reynales For- mation contains undescribed crinoids very similar to the Middle Ordovician crinoid Tornatilicrinus from the Leb- anon Limestone of Tennessee. Stipatocrinus hulveri gen. et sp. nov. is also inferred to represent a primitive but persistent Ordovician lineage. These taxa appear to rep- resent relict lineages that escaped Ashgillian extinction. Stipatocrinus hulveri formed monotypic, high-density as- semblages, suggesting that it may have acted as an op- portunistic species that thrived in physically stressed, un- crowded environments such as existed in the Early Silu- rian of the northern Appalachian Basin. These environ- ments may have provided a refuge for primitive holdover taxa that became extinct or were displaced coincidentally with an invasion of diverse Wenlockian echinoderm as- sociations that may nave evolved in the North American midcontinent (Witzke, Frest, and Strimple, 1979) or in presently unknown areas. Occurrence and Stratigraphy In 1983, while studying Early Silurian brachiopod com- munities in western New York, Michael Hulver of the University of Chicago discovered dolostone slabs covered with long crinoid stems from talus in the eastern side of the gorge of the Genesee River at Rochester, New York (Text-Figs. 1, 2). Subsequent investigation by Brett re- sulted in discovery of numerous nearly complete individ- uals of Stipatocrinus hulveri gen. et sp. nov. at this site, 0.3 km north of the lower falls of the Genesee River and 10 to 40 m east of the Rochester Gas and Electric access Oo km = 30 ———————— el, Toronto ONTARIO es Niagara Rochester ® Falls Conkey Ave. TeExtT-Fic. 1. Locality map of southwestern Ontario and western New York State. Arrow in inset at right indicates occurrence of Stipatocrinus hulveri gen. et sp. nov. Rochester lrondequoit Williamson Thorold sang Queenston TextT-FiG. 2. Upper Ordovician Queenston Formation and Silurian formations exposed in eastern side of gorge of Genesee River at Rochester, New York. Vertical section is approximately 50 m. Slabs bearing Stipatocrinus hulveri gen. et sp. nov. were found on talus slope between access road and Reynales Formation exposed in cliff. Arrows indicate lateral extent of occurrence. road south of Seth Green Drive, Rochester, Monroe County, New York (United States Geological Survey, Rochester West 7.5’ Quadrangle). Crinoid-bearing slabs appear to comprise parts of a large rockfall from the Wallington Member of the Reynales For- mation, exposed in the cliff above the talus (Text-Fig. 2). Laminated calcisiltite containing crinoids closely resem- bles that found interbedded with green shales near the base of the Wallington Member. Crinoid columns and distinc- tive t-shaped radials were obtained in situ from the lowest metre of this member, which probably represents the ho- rizon from which the study material was eroded. The Reynales Formation, also known as the Reynales Limestone, consists of complex, time-trangressive, dom- inantly carbonate strata extending from the Niagara area eastwards to near Wolcott, New York, where it grades laterally into the Bear Creek Shale. The Wallington Mem- ber (Fisher, 1960) is the uppermost unit of the Reynales Formation in the Rochester area. Approximately 4 m thick in the Genesee Gorge, the Wallington consists of thin- to medium-bedded, light grey, cherty, dolomitic limestone and dolostone with greenish-grey shale partings. Cross- lamination with a maximum amplitude of 2 cm occurs in calcisiltite (pelletal grainstone beds). Several horizons of fossiliferous packstone and grainstone within the Walling- ton contain abundant specimens of the brachiopods Pen- tamerus oblongus and Eocoelia hemispherica. On the basis of these brachiopods, the Wallington was considered to be of late Llandoverian (C,) age (Berry and Boucot, 1970). However, further consideration of brachiopod and cono- dont biostratigraphy led Rickard (1975) to propose an ear- lier (C,) age. Materials and Methods Most specimens of Stipatocrinus hulveri gen. et sp. nov. are embedded in a hard, dolomitic calcisiltite and proved difficult to prepare. Attempts to remove matrix, using so- dium bicarbonate in an airbrasive machine, were not suc- cessful. Dolomite powder proved to be an effective abrasive but readily damaged the thin plates of these crinoids. For- tunately a few specimens, including the holotype, are embedded in a softer, slightly argillaceous matrix and were prepared using needles and airbrasion with little damage. Immersion of specimens in ethanol facilitated morphologic study. Text-Figures 5, 6, and 7 were prepared by tracing over photographs. Plate dimensions were measured using vernier Calipers; orientations of these plates are given in Table 1: All study material is deposited in the collections of the Department of Invertebrate Palaeontology, Royal Ontario Museum (ROM) in Toronto, Ontario, Canada. Systematic Palaeontology Class Crinoidea Miller, 1821 Subclass Camerata Wachsmuth and Springer, 1885 ?Order Monobathrida Moore and Laudon, 1943 Superfamily Stipatocrinacea superfam. nov. DIAGNOSIS Lowest circlet in cup consisting of four plates (basals?); two large plates adjacent to one another along C-ray suture and two small plates directly in line with A- and E-ray radials. This circlet divided by sutures in AB-, DE-, and EA-interrays. Radials and fixed brachials narrow, elon- gate, raised. Primanal and anitaxis absent. Interbrachials small, exceptionally numerous, irregular in shape and arrangement. Family Stipatocrinidae fam. nov. DIAGNOSIS Characters of superfamily. Stipatocrinus gen. nov. TYPE SPECIES Stipatocrinus hulveri sp. nov. ETYMOLOGY From the Latin stipatus—crowded—in reference to the numerous interbrachials crowded together in the interrays, and from the Greek krinon—lily. DIAGNOSIS Monotypic genus of Stipatocrinidae with narrow conical cup and depressed interrays. Radials t-shaped, bridging interrays. Primibrachials two in each ray, elongate, straight sided, grooved ventrally. Fixed secundibrachials four to iA > Ca ‘acs o> oe hs 20, LIS SY) rH 2 RT B ree Z < KORA TEXT-FiG. 3. Plate diagram of Stipatocrinus hulveri gen. et sp. nov. Note peculiar configuration of proximal circlet, divided into bilaterally symmetrical halves by sutures in AE-interray and C-ray. The t-shaped radials (black) enclose suboval interbrachial areas and are smaller in BC- and CD-interrays than in remaining interrays. six in each ray branch. Fixed pinnule borne by second secundibrachial. Interbrachials smooth, without ornamen- tation. Narrow cylindrical anal tube eccentrically located on tegmen. Arms ten, pinnulate; brachials in immature biserial arrangement. Column transversely circular. DISCUSSION There is little doubt that Stipatocrinus gen. nov. belongs to the subclass Camerata in view of its densely pinnulate arms, fixed ray series, fixed pinnules, and numerous in- terbrachials. However, below this level, classification be- comes difficult. It is not clear whether Stipatocrinus should be classified among the Monobathrida or the Diplobath- rida, or in a separate order altogether, because the peculiar plate configuration of the base of the cup in this crinoid renders plate homologies obscure. The problem is com- pounded, for the column of Stipatocrinus is neither pen- tameric nor pentagonal, but cylindrical with a round lumen. Hence, this column does not provide any indication of orientation of thecal plates relative to the entoneural sys- tem, as suggested by the “‘Law of Wachsmuth and Spring- er’ (Warn, 1975). Even the location of radials in Stipatocrinus 1s somewhat problematic. The A- and E-rays are each supported by a single uninterrupted row of plates beginning in the lowest circlet of the cup (Text-Fig. 3). Thus, plates of this circlet in the A- and E-rays could be considered to be radials. However, if this interpretation is followed, the radials of these rays would lie immediately above the stem facet, a feature unknown in all other crinoids. In the B-, C-, and D-rays the lowest plates of the rays are t-shaped and sit- uated within the second circlet of plates (Text-Fig. 3). These t-shaped plates are relatively narrow, as in fixed brachials, and are even grooved ventrally (Pl. 1, figs. 16,20). However, they are differentiated from all other cup plates by their lateral processes, and they form a dis- tinctive circlet. We feel fairly confident in designating plates of the second circlet as radials because a t-shaped plate of the C-ray overlies a suture between plates of the lowest circlet. This plate is therefore in typical radial po- sition. Furthermore, the strong differentiation of these plates is also suggestive of radials. In other primitive camerate crinoids, including reteocrinids and xenocrinids, the ra- dials are always markedly separate from other adjacent plates (Brower, pers. comm., 1986). Configuration of the lowest circlet of cup plates in Sti- patocrinus is unique among camerate crinoids, both in terms of the shapes and relative sizes of these plates and, most notably, in their orientation with respect to the ra- dials. The lowest circlet combines features of infrabasals, basals, and radials. Three of four sutures dividing this circlet are interradial (AB-, DE-, and EA-interrays), a characteristic of infrabasals; the fourth suture is directly below the C-ray radial as it would be in a normal basal TEXT-FiG. 4. Stipatocrinus hulveri gen. et sp. nov. Specimens immersed in ethanol. A. Individual centred on C-ray. Proximal circlet is divided by suture in C-ray but not in BC- or CD-interrays. Aborally directed bifurcation of C-ray ridge continues on basals. Small suboval interbrachial areas in BC- and CD-interrays, bounded above by t-shaped radials, are of similar size. Interbrachials, underlain by black integument, are poorly preserved. Paratype ROM 44309a, x 4.0. B. Individual centred on D-ray. Proximal circlet is divided by suture in C-ray and DE-interray but not in CD-interray. Sub- oval interbrachial area in DE-interray, bounded above by t-shaped radials, is smaller than adjacent area in CD-interray. Interbra- chials are well preserved in this specimen, and proximal portion of anal tube is visible. Paratype ROM 44309b, x 4.0. circlet (Text-Figs. 3, 4A,B). Furthermore, two plates in the lowest circlet resemble radials because they are directly in line with and support the A- and E-rays. An unusual and interesting feature of Stipatocrinus is that the plates of the lowest circlet are dissimilar in size and shape with respect to each other. Two plates of this circlet, directly in line with the A- and E-rays, are five- sided and considerably smaller (narrower) than the larger six-sided plates that they adjoin laterally (Text-Fig. 3). Pairing of each larger plate with a smaller one divides the lowest circlet into bilaterally symmetrical halves, each with two plates, about a sutural plane passing through the AE- interray and C-ray. To our knowledge, no other camerate crinoids, including xenocrinids, possess a basal circlet with this symmetry. We emphasize that the peculiar configuration of the lowest circlet of cup plates in Stipatocrinus is not an ab- normality. Consistent orientations have been observed in all seven specimens that have been adequately prepared. Furthermore, plate organization appears well coordinated with ray ridge configuration. an Homology of the lowest circlet of cup plates in Stipa- tocrinus is a problem. We have termed these plates basals because they comprise the only circlet of plates between the stem facet and inferred radial circlet. However, the proximal circlet resembles a typical basal circlet only at the C-ray suture, situated directly below the C-ray radial. An alternative interpretation is that the lowest circlet of plates in Stipatocrinus may be homologous with the in- frabasals of dicyclic camerates, in which the sutures are invariably interradial in position. However, number and sutural configuration of plates in the lowest circlet of S1- patocrinus do not precisely conform to that of a normal camerate crinoid infrabasal circlet. Nearly all diplobath- rans possess five equal infrabasals, although the Anthemo- crinidae possess four. None of these crinoids has a suture in the C-ray position as in the Stipatocrinus base. Instead, sutures between infrabasals normally occur in the BC- and CD-interrays; such sutures are absent in Stipatocrinus (Text- Figs. 3, 4A). The origin of the unequal basals in Stipatocrinus 1s un- clear. The infrabasal circlet of anthemocrinids, a family unrelated to Stipatocrinus, possesses a large plate presum- ably derived from fusion of two smaller plates. In contrast, Stipatocrinus possesses two large and two small plates in the lowest circlet. The two large plates could have devel- oped by lateral fusion of two pairs of plates in an infrabasal circlet that originally possessed six plates. However, this seems unlikely, for crinoids with six infrabasals are un- known. A more plausible explanation is that the two larger plates of Stipatocrinus were derived in two different ways: one by fusion of two plates, the other by enlargement of a single plate, so that the sutural position migrated from an interradial to a radial position. This would imply an ancestral condition with five plates in the lowest circlet, for which no evidence exists. If the lowest cup plates of Stipatocrinus are homologous with infrabasals, we are faced with the obvious problem of absence of a basal circlet. Most researchers have implied that a pseudomonocyclic condition results from loss of infrabasals (Warn, 1975; Ubaghs, 1978). For example, the inadunate genus Jocrinus could have evolved from Mer- ocrinus by loss of infrabasals. Alternatively, certain mon- ocyclic inadunates including Belemnocrinus may have evolved from dicyclic forms by loss of the basal circlet (McIntosh, 1979). The latter process may also have oc- curred in Stipatocrinus. The interrays of Stipatocrinus are peculiar in several respects. Most notably, they are filled with an exceptional number of small ossicles, more than 400 plates in the CD- interray of the holotype specimen (ROM 44310a, Pl. 1, figs. 1,3). Moreover, these plates are irregular in size, shape, and arrangement and are unusually thin. Unlike the majority of camerate crinoids, Stipatocrinus has interrays without a well-developed gradient of progressively smaller plates distally. Finally, Stipatocrinus lacks a primanal and anitaxis but possesses a cylindrical anal tube composed of plates resembling interbrachials. Moore and Laudon (1943) considered small, irregular, and numerous interbrachials to be a primitive character. Brower (1974a) believed this characteristic to be advanced in xenocrinids, crinoids with interray plating similar to Stipatocrinus and occurring stratigraphically above sup- posedly related camerates with fewer and larger interbra- chials. However, this conclusion was based, in part, on a misinterpretation of the phylogeny of xenocrinids (Brower, pers. comm., 1986). Poorly known phylogenies of ca- merate crinoids do not prove that either of these conflicting theories is correct. However, we believe that ontogenetic patterns of growth in primitive pelmatozoans and biostrati- graphic evidence lend support to the Moore and Laudon hypothesis. Ontogeny of interbrachials in most camerate crinoids was closely integrated and coordinated with increase in size of the cup (Brower, 1974b). Originating near the periphery of the tegmen, interbrachials were derived from tegmen interambulacrals that were modified in size and shape, becoming regular polygons as they were gradually incorporated into interrays. Consequently, interrays of most camerate crinoids typically show a well-developed gra- dient of progressively smaller and more irregular inter- brachials towards the tegmen. This gradient apparently evolved early in the history of camerates, first appearing in the Lower Ordovician crinoid Proxenocrinus. Unlike that of most crinoids, ontogeny of interbrachials in Stipatocrinus and the Late Ordovician crinoid Xeno- crinus was poorly coordinated and poorly integrated with overall growth of the cup. In these crinoids, interbrachials grew more slowly than other calyx plates, necessitating an intercalatory mode of growth (Brower, 1974a). As a consequence of this mode of growth, interbrachials in Sti- patocrinus and Xenocrinus are irregular in shape and ar- rangement. Interbrachials could have been added anywhere within interrays of these crinoids. This pattern 1s especially ‘well developed in Stipatocrinus, in which small interbra- chials adjacent to larger interbrachials are scattered throughout interrays. Intercalation increased the number of interbrachials at a given level within the cup as this crinoid grew. New interbrachials were also added by in- corporation of interambulacrals. Interbrachials in Stipa- tocrinus merge smoothly into the tegmen, indicating that tegmen plates were incorporated into interrays, unaccom- panied by substantial modification in size or shape of these ossicles. Because of an intercalatory mode of growth, in- terrays of Stipatocrinus and Xenocrinus display a poorly developed gradient of progressively smaller plates distally. The origin of camerate crinoids and their relationships to other groups of pelmatozoans is poorly known. How- ever, biostratigraphic evidence indicates that primitive Cambrian pelmatozoans, including the probable crinoid Echmatocrinus, are characterized by thecae possessing a large number of plates irregular in shape and arrangement. Moreover, thecae of these echinoderms typically show a poorly developed gradient of progressively smaller plates distally, and these plates commonly merge into the tegmen with little differentiation. We suggest that similar features in Stipatocrinus represent primitive characters. The calyces of Stipatocrinus and Xenocrinus are similar in that both possess large numbers of small irregular in- terbrachials. However, Xenocrinus has a well-developed anitaxial ridge, and configuration of the lowest circlet of plates in Stipatocrinus is unlike that of Xenocrinus. We conclude that similar morphology of interrays suggests simply that these crinoids belong to archaic lineages prob- ably not closely related to each other. In fact, superficial similarity of these genera could be an example of con- vergent evolution, although this possibility seems doubt- ful. It implies repeated development of large numbers of small interbrachials from ancestors with larger regular in- terbrachials, which is contrary to evolutionary trends in camerate lineages of simplifying cup structure by reducing numbers of interbrachials or eliminating them altogether. Even the assumption that Stipatocrinus 1s related to di- plobathran camerates does not provide insight into the evolution of this genus. Gaurocrinus and Reteocrinus, both members of the Reteocrinidae, possess large numbers of irregular interbrachials as in Stipatocrinus. However, these crinoids have a primanal within the radial circlet and also possess a prominent, ridged anitaxis. Furthermore, Reteo- crinus has divergent characters, including interinfrabasal gaps, spiculelike interbrachials, and apinnulate, branching arms. None of the more advanced diplobathrans is at all similar to Stipatocrinus. Thus, Stipatocrinus presently stands by itself. We follow convention in tentatively assigning this genus to the Monobathrida because only a single circlet of plates is situated below the radials. However, we also emphasize that the present monocyclic-dicyclic schism in classification of crinoids, discussed by Warn (1975), may obscure phylogenetic relationships. In fact, Stipatocrinus may belong to a sister group of the Diplobathrida. Dis- covery of additional genera related to Stipatocrinus may readily justify erection of a new order to encompass these unusual crinoids. We conclude that the several seemingly primitive features of Stipatocrinus suggest that it may have been a “‘living fossil’’ in late Llandoverian seas. Stipatocrinus hulveri sp. nov. Text-Figs. 1-8; Pl. 1, figs. 1-21; Pl. 2, figs. 1-12 TYPE MATERIAL Numbered slabs containing approximately 75 calyces and crowns associated with numerous columnals and columns of this species are deposited in the collections of the De- partment of Invertebrate Palaeontology at the Royal On- tario Museum, catalogue numbers ROM 44309-44344. Figured specimens: holotype ROM 44310a; paratypes ROM 44309a,b,d; 443 10b-44323. OCCURRENCE Reynales Formation, Wallington Member, exposed in the gorge of the Genesee River, Rochester, New York. ETYMOLOGY The species is named in honour of Michael Hulver. DIAGNOSIS As for genus. DESCRIPTION Calyx steeply conical (height/width = 1.5—1.7), with highly elevated ray ridges and depressed interrays. CD-interray about 20 per cent wider than other interrays. Four plates in lowest cup circlet, here designated as basals, possibly representing infrabasals. Proximal circlet comprising approximately I5 per cent of calyx height, divided by sutures in AB-, DE-, and EA-interrays and in C-ray, undivided in BC- and CD-interrays (Text-Figs. 3, 4A,B; Pl. 1, figs. 1,5,6,13—15). Basals two large and two small (Pl. 1, fig. 13). Basals directly underlying A- and E-ray radials five-sided, smaller (narrower) than larger six- sided basals occupying AB- through DE-interrays (Text- Figs. 3, 4A,B, 7; Pl. 1, figs. 5,6). Smaller basals elongate, widest just above stem facet (PI. 1, fig. 5). Larger basals expanding in width distally. Sutures passing through AE- interray and C-ray divide basal circlet into bilaterally sym- metrical halves (Text-Fig. 3). In AB-, DE-, and EA- interrays basals meeting along straight suture for about one-third to one-half of basal height, diverging above forming concave margins of proximal interrays (Text-Fig. 3; Pl. 1, fig. 5). In BC- and CD-interrays these concave margins less pronounced, not extending as close to stem facet (Text-Figs. 3, 4A). Basals in A- and E-rays each with ridge continuing onto A- and E-ray radials, respec- tively. Larger basals meeting directly below C-ray along straight suture for about 80 per cent of basal height, each possessing two adradially directed ridges. Pair of ridges divided by suture separating these basals merging up- wards, forming single ridge on C-ray radial (Text-Figs. 3, 4A). Radials and higher fixed brachials grooved ventrally (PI. 1, figs. 16,17,20,21), extremely narrow, forming highly elevated ray ridges extending full width of brachials (Text- Figs. 3, 4A,B, 8; Pl. 2, figs. 1-5). Radials t-shaped (height/ maximum width = 1.6—1.8). Each radial bisected near midpoint by pair of short, narrow, laterally directed pro- jections (Text-Figs. 3, 4A,B; Pl. 1, figs. 5,20). Projections forming ridges lower in height than ray ridges, crossing proximal interray areas, narrowly joining radials together. First primibrachials rectangular, highly elongate (height/ width = 3.0—5.0), straight-sided. Second primibrachials Y-shaped (height/width = 1.4—1.6), axillary (Pl. 1, fig. 10). Each ray bifurcating near centre of second primibra- chial, forming two straight ray ridge segments continuing upwards towards arms. First secundibrachials rectangular (height/width = 1.5—1.9), each bearing a stout fixed pin- nule bounded by interprimibrachials (PI. 1, figs. 1,4). Sec- ond secundibrachials equidimensional (height/width = 1.0). Succeeding fixed secundibrachials rectangular, wider than high (height/width = 0.6—0.8). Arms free beyond third to seventh secundibrachial. Interrays filled with exceptionally numerous interbra- chials (more than 400 ossicles in CD-interray of holotype specimen, ROM 44310a; PI. 1, fig. 1). Interrays of smaller individuals with fewer plates (Pl. 2, figs. 10,11). Inter- brachials immediately above basals enclosed in suboval to subtriangular depressed areas bounded above by lateral projections of radials (Text-Figs. 3, 4B, 5; Pl. 1, fig. 19). These enclosed areas smaller in BC- and CD-interrays than in remaining interrays (Text-Figs. 3, 4A,B; Pl. 1, fig. 6). Interbrachials irregular polygons, typically five- or six- sided, varying from four- to seven-sided. Largest inter- brachials commonly with rounded corners. Interrays dis- playing poorly developed gradient of progressively smaller plates distally; smaller plates occurring between larger plates throughout interrays (Pl. 1, fig. 3). Interbrachials smooth, without ornamentation, very thin (approximately 0.03 mm thick), resting on black layer representing degraded or- ganic matter (Text-Figs. 3, 4A; Pl. 1, fig. 5). Interray areas loosely sutured to straight-sided ray series. Primanal and anitaxis absent. Narrow cylindrical anal 1 m m , i TextT-Fic. 5. Plate diagram of basals and proximal interbra- chials in AB-interray of Stipatocrinus hulveri gen. et sp. nov. Paratype ROM 44310b, PI. 2, fig. 19. tube developed in CD-interray, eccentrically situated near edge of tegmen (PI. 1, figs. 1,11; Pl. 2, figs. 1,9). Anal tube incompletely preserved in available specimens, com- posed of smooth polygonal plates resembling interbrachi- als (Text-Fig. 6; Pl. 1, figs. 2,4). Tegmen seen only in cross-section, forming shallow dome consisting of polygonal plates resembling interbra- chials in size and shape. Some tegminal plates nodose, commonly bearing short spines (PI. 1, fig. 12). Arms ten, pinnulate, relatively long (Table 1). Proximal brachials in uniserial arrangement (PI. 1, fig. 5), rectan- gular, wider than high (height/width = 0.4—0.6). Suc- ceeding brachials cuneate, in immature biserial arrangement in distal portions of arms (PI. 1, fig. 8). Pinnules incom- pletely known. Pinnulars attached directly to free brachi- TEXxT-FiG. 6. Plate diagram of anal tube of Stipatocrinus hul- veri gen. et sp. nov. Anal plates resemble interbrachials. Dotted area represents area damaged during preparation. Holotype ROM 44310a, Pl. 1, fig. 2. als, short, quadrangular, tapering distally (Pl. 1, fig. 7). Succeeding pinnules lath-shaped (height/width = 2.2—2.7). Column transversely circular, heteromorphic, tapering uniformly almost to a point distally (Pl. 2, figs. 4,5,8,10). Proximal nodals biconcave in longitudinal cross-section with thickened, rounded epifacets concealing adjacent in- ternodals (Text-Fig. 7A,B; Pl. 1, fig. 18). Internodals rec- tangular or slightly biconvex in longitudinal cross-section. Proximal columnals thin (nodal height/width = 0.25—0.33, internodal height/width = 0.06—0.13). Columnals becom- ing successively thicker in distal portion of column (nodal height/width = 0.28—0.36, internodal height/width = 0.17— 0.22). Noditaxis typically consisting of one nodal, two or three second-order internodals, a first-order internodal, and two or three second-order internodals (Text-Fig. 7A—D). Lumen small, round (PI. 2, figs. 6,7). TABLE 1. Measurements (in mm) of types of Stipatocrinus hulveri gen. et sp. nov. Orientation of plate measurements as follows: ROM 44309a—below B- and C-rays (basal), C-ray (radial— secundibrachial); RoM 44309b and 44310a—below C- and D-rays (basal), D-ray (radial—secundibrachial); ROM 44310b—below B- and C-rays (basal), B-ray (radial—secundibrachial). Paratype Measurements ROM 44309a Calyx height 13.7 Calyx width ll Arm length 33.07 Proximal stem diameter Het) Basal height 2.1 Basal width 2.1 Radial height 37 Radial width Dal First primibrachial height 2.8 First primibrachial width 1.0 Second primibrachial height 2.4 Second primibrachial width 1.8 Second secundibrachial height 1.4 Second secundibrachial width 1.0 *Specimen crushed. Actual width less than indicated. tDistal portions of arms not preserved. 1mm aes | \ =z ND z Paratype Holotype Paratype _ ROM 44309b ROM 44310a _ ROM 44310b 14, 1 18. 4 N32 Sa 10.5* a — ss 18.07 2.8 3.1 Pes) 1.9 DD eS) 1.9 DS) DS) 3.6 3.8 3)-5) si 2.0 we i) 3.6 3.8 32) 2 2. 0.89 Dell 2.9 DS) 1.9 2.0 IES 1.6 2.0 1.4 0.97 1.0 0.81 a IN Diss IN ‘ alex IN rake “8 C D TEXT-FiG. 7. Diagrams of longitudinal cross-sections through pluricolumnals of Stipatocrinus hulveri gen. et sp. nov. Nodals and internodals are indicated, respectively, as follows: N, 1 IN, 2 IN, 3 IN. A. Pluricolumnal between 9 and 10 mm below cup of paratype ROM 44319, indicated by upper pair of arrows on PI. 1, fig. 18. Very thin second-order internodals are not visible from exterior of proximal column. B. Pluricolumnal between 26 and 28 mm below cup of paratype ROM 44319, indicated by lower pair of arrows on PI. 1, fig. 18. Second-order internodal is incipient nodal. Note prominent, thickened epifacets of nodals, which partly enclose adjacent third-order internodals. C. Distal pluricolumnal of paratype Rom 44320, indicated by upper pair of arrows on PI. 1, fig. 9. D. Distal pluricolumnal of paratype ROM 44320, indicated by lower pair of arrows on PI. 1, fig. 9. 9 Palaeoecology Limited lateral extent of slabs bearing Stipatocrinus hul- veri on a talus slope in the gorge of the Genesee River and apparent absence of similar slabs in the cliff wall above indicate that these crinoids comprised a highly localized stand, or “‘garden,’’ on the seafloor. The area of seafloor occupied by this stand, assuming that the majority of spec- imens have been discovered, did not exceed 0.2 m?. This occurrence represents a high-density stand (sensu Brower, 1973) with about 400 crinoids per square metre. Few fos- sils, including poorly preserved specimens of the brachio- pod Coolinia? and encrusting bryozoans are associated with these crinoids (PI. 2, fig. 10). The horizon from which the Stipatocrinus material was apparently derived is nearly devoid of fossils, indicating that the seafloor surrounding this stand was sparsely populated by skeletonized benthic organisms. Stands of Early Silurian crinoids described by Brett (1978) and Eckert (1984) also occur in poorly fos- siliferous strata. Clustering of conspecific crinoids in these environments may have conferred adaptive advantage by providing viable breeding populations (Brower, 1973). Polished slabs obtained by sectioning perpendicular to bedding planes reveal that well-preserved Stipatocrinus individuals consisting of nearly complete crowns with long stems occur in calcisiltite adjacent to a thin encrinite (Text- Fig. 8). Although it is not possible to demonstrate con- clusively the sequence of deposition of these layers be- cause the slabs were not recovered in situ, comparison with stands of Early Silurian crinoids excavated in situ (Eckert, 1984) and personal observations of occurrences of well-preserved crinoids in the Middle Devonian Ham- ilton Group of western New York and Ontario strongly suggest that well-preserved Stipatocrinus individuals are situated immediately above the encrinite. Consisting al- most entirely of Stipatocrinus columnals, cup plates, and arm fragments, the encrinite rests with a sharp lower con- tact on plane-laminated, unfossiliferous calcisiltite. Com- TeEXxT-Fic. 8. Vertical section through slab containing Stipa- tocrinus hulveri gen. et sp. nov. Basal encrinite (En) is inferred to represent lower surface of slab. Calcisiltite layer (Ca) above encrinite shows well-preserved, sectioned cups and pluricol- umnals of S. hulveri. Paratype ROM 44322. plete calyces, typically lacking arms and columns, are embedded in the lower surface of this encrinite. In reconstructing the palaeoecology of this occurrence, we infer that the Stipatocrinus hulveri stand originated from a chance spatfall on a sparsely populated seafloor. Most of these pioneer individuals attained maturity, as indicated by the large size of radials in the encrinite (PI. 1, fig. 20). Death, decay, and subsequent disarticulation of these crinoids under conditions of generally slow sedi- mentation gradually formed a carpet of ossicles, repre- sented by encrinite, below the stand. Resuspension of ossicles by currents buried decaying, partly articulated, individuals relatively quickly. Small crinoids, evidently juveniles, associated with larger individuals indicate that the stand survived for more than one generation. Even- tually the stand was completely extirpated by rapid burial, indicated by excellent preservation of articulated crinoids in calcisiltite, displaying undulatory laminations. Burial must have been rapid because modern crinoids exposed on the seafloor typically decay and disarticulate quickly after death (Meyer, 1971; Liddell, 1975; Meyer and Meyer, 1986). In the Reynales Formation at Rochester, beds of Pen- tamerus, a brachiopod that inhabited relatively shallow, rough-water environments (Boucot, 1975; McKerrow, 1978) alternate with sparsely fossiliferous strata deposited in rel- atively quiescent, probably deeper water conditions. Thus, occurrence of well-preserved Stipatocrinus specimens in sparsely fossiliferous strata lacking Pentamerus is con- sistent with a previous interpretation (Brett and Eckert, 1982) that occurrences of well-preserved crinoids are typ- ically associated with quiet-water palaeoenvironments near the limit of normal wave base but within reach of storm- generated waves and currents. Several slabs bearing S. hulveri show prominent, subparallel orientation of crowns and columns suggestive of storm-generated currents during or immediately preceeding burial (PI. 2, figs. 10,12). After burial the crinoids rapidly decayed, but disarticulation was prevented by overlying sediment and absence of biotur- bation. Internal organs were not preserved in any speci- mens of Stipatocrinus. However, a black carbonaceous film representing degraded organic matter commonly cov- ers inner surfaces of interbrachials (Text-Figs. 3, 4A; Pl. 1, figs. 5,11). A reducing, acidic environment was ap- parently generated within the calyces as decay proceeded, inducing formation of syngenetic pyrite on some speci- mens. Acidic conditions caused dissolution of interbra- chials in some individuals (Text-Figs. 3, 4A; Pl. 1, figs. 5,11). Dissolution probably occurred before lithification because the crinoids are not preserved as steinkerns. Many Stipatocrinus calyces are filled with sparry cal- cite. These specimens are typically less crushed or flat- tened than individuals filled with calcisiltite. Precipitation of calcite within hollow calyces early in diagenesis may have allowed the crinoids to resist compaction (see Sprin- kle and Longman, 1982:69). However, it is also possible that calcite was precipitated late in diagenesis after lithi- fication. When calcite was absent, thinly plated interrays of Stipatocrinus made these crinoids susceptible to com- paction, distorting and flattening them. Densely pinnulate arms and the flexibility of the prox- imal portion of the column suggest that Stipatocrinus was a rheophilic filter feeder. The t-shaped radials that bridge proximal interray areas helped to strengthen the base of the calyx. However, narrow brachials and unusually thin interbrachials that do not interlock with the ray series made the Stipatocrinus calyx relatively fragile in construction when compared to most other camerates, perhaps restrict- ing this crinoid to relatively low-energy environments. Apparent absence of Stipatocrinus in the Pentamerus com- munity is consistent with this interpretation. Extremely narrow fixed brachials and t-shaped radials made possible incorporation of more interbrachials in Sti- patocrinus than any other described crinoid of similar size. Functional morphology of this interray plating is conjec- tural. The ease with which Stipatocrinus calyces were flat- tened during compaction of the sediment, without breakage of plates, demonstrates that the interrays were flexible in life. Brower (1974a) postulated that large numbers of in- terbrachials in Xenocrinus aided respiration by diffusion of oxygen through plate sutures, enhanced by pumping action of flexible interrays. Perhaps oxygen could diffuse directly through the unusually thin (0.03 mm thick) inter- brachials of Stipatocrinus. We note, however, that unlike certain Ordovician crinoids with pore-bearing calyces, there is no evidence of auxiliary respiratory structures in Early Silurian crinoids. Numerous interbrachials in Stipatocrinus may simply be a scaling phenomenon involving thickness/ width ratios of plates: reduction in plate thickness neces- sitated smaller plate size in order to retain resistance to breakage. Unusually thin interray plating and a thick but very narrow fixed ray series of the calyx of Stipatocrinus in- corporated the smallest amount of calcite possible con- sistent with requirements for sufficient strength and rigidity. Thus, metabolic cost of calcite secretion in Stipatocrinus was minimal compared to most other thicker-plated cri- noids. By reducing metabolic cost, overall growth of Sti- patocrinus may well have been rapid, perhaps allowing early reproduction. If Stipatocrinus is assumed to have colonized environments generally unfavourable to most crinoids, as occurred during deposition of the lower Wal- lington Limestone, an r-selective strategy of early repro- duction may have ensured survival. The column of Stipatocrinus 1s relatively short, not ex- ceeding 10 cm in length, and tapers gradually almost to a point distally. Curvature of the distal portion in paratype ROM 44314 (PI. 2, fig. 8) and in other specimens suggests that the column of Stipatocrinus was coiled distally around other objects for anchorage. This mode of attachment is characteristic of many camerates with gradually tapering, heteromorphic columns, including Alisocrinus, Glypto- crinus, Xenocrinus, and most diplobathrids (Brett, 1981). Possession of a distally coiled column permitted attach- ment to a wide variety of substrates (Brett, 1985) and was probably a contributing factor in the survival of melocrin- itids, glyptocrinids, dimerocrinitids, rhodocrinitids, and the lineage leading to Stipatocrinus into the Silurian. Acknowledgements Diligent field work by Michael Hulver resulted in discov- ery of the study material, and we are indebted to him for making us aware of this occurrence. Additional specimens were collected by Gordon Baird and Karla Parsons. George C. McIntosh, James Brower, and James Sprinkle critically reviewed the manuscript. Janet Waddington of the De- partment of Invertebrate Palaeontology at the Royal On- tario Museum provided curatorial services. Darkroom and preparation facilities were provided by the Department of Geological Sciences at the University of Rochester. Fi- nancial support for this study was provided by the Geo- logical Society of America as grant 3288-84 to Eckert. oe jae? 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Arvo 4 Meas Nl earn tidewdtd roe Bt ou aa sats iy ciiey hin ere useritite side uit tsinaetray 7 ji edeerets (his yh a eecematenreiis trenwtan pie itt ary Avis ae bcvnttiass * \ wih ait oe ny peethiad ta) dni Ce vis aha Zyl deminc aie hebabindin wey vines dheeh.t (G00 fy! nails dire vlad Kaka yh i Mi my ta-@y ia 1 : J IFS We Ne onal ihren Lies botearae wendy aie gt ia tinal fx y) iphecid wih ‘ad ata | eceeaal bruh ul “it ‘¢ ‘iui ag NE. ‘Watial eet aed cull ntnigtoue ii ty oe at pies" ' curiae tarts 4 aToqnar te A wn ey ft! — OnE ‘rat ith rye md a - ~s opvetuer ty wlitas wl Bk ie a Ce me Minin to Dini ts tease es ces sdbeaies rua dye Gat : “} a kin ta ccm th ag 7 xe Peanl all > Sy 0 rv with its ethervas Goan ea ae UAE A HATED eanINT TER) (2 dole dit ae on . tulvins pie aban ! “were Saw jive ath vga? meee ieee he ir lice atin ee ¥ peer y' uted rhplvw qusds Vint ve whores udil> (i pbelignel pf came Y Lena iL} salted ——_ pee ipa A Aire re 730 wentrraie wytel aes Te man hotpll rote peeniolen . j , ide, vel walle i fvalilhs ened ana id “ Tey | Ato, Oi) 7 fern eayugp: yt bed ee | dre anlige ohuy it uve iv iwi , : say eft ieaewuy | ; “aw itt: une! cope pieguinT 5 in yf idhaaniied med © i ; 4) lina a an es ride ra nye fit y tah —iyL Sapa owt. 1 ow ndoniennborntiey vo ‘J litt tacit coveted oneal tens , va “ . \ bball), biveve lacs tors yea wail finales: hanno) pati - , . excised With Qulet-aalier pelea overuse } ve “oupey Sil t vit neh iW - | p { vents ie sate nt ‘abe’ mG - Ly? f : ut pil tel 7 aon ' : ; hes | it ie . iP a hen ry 4) aye Ths , yf ti wt y wh iit} iP iF (i beat uy a wa {tat gre “ih . : ' _? icy Lod Liesl j (it ‘si QW iyi oft oa een ‘! . we } : ps pity. f nt lj ipilglas neni | ) aniccinl Th tmeat NU Poh Wid, ~_ ~ ah. - srs | Tey] [feu Laie RECA AR ieee nv J ats wi | el ot) sul) Te Awoberth bait, Sori ha TL \ aah 57 whl at ar. im i e a “0 j 7 Avy. ola wn ne ster a 0 9y stat i uCwhe callie iu sia on aoe i fen untal ' i a ada levy ar: | Ve twa pA ive Wied t , oy Sey if ie, ad) be pin atte de pine i, in Ce _ > g, — a Literature Cited AUSICH, W. 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STRIMPLE 1979 Biogeography of the Silurian-Devonian echi- noderms. /n Gray, J. and A. J. Boucot, eds., Historical biogeography, plate tectonics, and the changing environment. Corvallis, Oregon State University Press, pp. 117-129. WITZKE, B. J. and H. L. STRIMPLE 1981 Early Silurian camerate crinoids of eastern lowa. lowa Academy of Science, Proceedings 88:101— 37. 13 PLATE 1, figs. 1—21. Stipatocrinus hulveri gen. et sp. nov. Reynales Formation, Rochester, New York. Specimens immersed in ethanol. 1. CD-interray of well-preserved individual. Note absence of primanal and anitaxis. Proximal circlet is divided by suture in DE-interray but not in CD-interray; t-shaped radials bridge proximal interray areas, enclosing interbrachials between basals and lateral projections of radials. Narrow, highly raised brachials enclose thinly plated interrays consisting of numerous, polygonal interbrachials. Distal interbrachials merge with plates of anal tube and tegmen without differentiation. See also Text-Fig. 6; Pl. 1, figs. 24,10; Pl. 2, fig. 1. Holotype Rom 44310a, x 3.5. 2. Cylindrical anal tube of above individual showing arrangement of irregular polygonal plates. Distal portion of tube is missing. See Text-Fig. 6 for a diagram of this specimen. Holotype Rom 44310a, x 8.0. 3. CD-interray detail between first primibrachial and second secundibrachial. Interray, slightly separated from C-ray in this individual, is composed of numerous polygonal interbrachials irregular in shape and arrangement. Holotype ROM 44310a, x 7.0. 4. C-ray and adjoining interbrachials showing proximal portion of anal tube and first pinnular of fixed pinnule borne by second secundibrachial. Holotype Rom 44310a, x 7.0. 5. Anterior view of nearly complete crown. Orientation of rays unknown. Interbrachials, apparently dissolved during diagenesis, are absent in most of interray area, revealing underlying black layer representing degraded organic matter. Interray areas below lateral projections of radials are subtriangular in this specimen. Proximal free brachials are uniserial. See also Pl. 2, fig. 12. Paratype Rom 44311f, x 3.0. 6. Specimen centred on B-ray. Numerous irregular polygonal interbrachials are visible in BC-interray. Basal circlet is divided by suture in AB-interray but not in BC-interray. See also Text-Fig. 5; Pl. 1, fig. 19; Pl. 2, fig. 3. Paratype Rom 44310b, x 4.0. 7. Proximal arm detail. Note short pinnules. Paratype ROM 44321, x 5.0. 8. Distal portion of arm with cuneate brachials. Paratype RoM 44309d, x 5.0. 9. Longitudinal cross-section through distal column. Nodals have prominent, thickened epifacets. Typical noditaxis consists, sequentially, of a nodal, two or three second-order internodals, a first-order internodal, and two or three second-order internodals. See Text-Fig. 7C,D for diagrams of two noditaxes indicated here by pairs of arrows. Paratype ROM 44320, x 4.0. 10. Intersecundibrachial detail between bifurcation of D-ray. Holotype Rom 44310a, x 6.0. 11. CD-interray of crown. Incomplete anal tube is outlined by black integument. Most interbrachials are missing. See also Pl. 2, fig. 12. Paratype ROM 4431la, x 2.0. 12. Longitudinal cross-section through distal fixed secundibrachials and tegmen. Many tegminal plates possess nodes or short spines. Paratype ROM 44315, x 6.0. Figs. 13-16. Sequential series of cross-sections through lower portion of cup destroyed by progressive grinding. C-ray is at upper left of each section. 13. Basals just above stem. Note small opening for lumen. Basal suture at upper left is directly below C-ray. Two basals below B-, C-, and D-rays are larger than remaining basals. 14. Slightly higher section through basals showing initial development of ridges on rays. 15. Basals sectioned near top of cup with prominent ridges on rays. 16. Section through proximal portions of radials and interrays. Each radial has prominent ventral groove. 17. Cup transversely sectioned just below bifurcation of rays. Cup has been strongly compressed, dem- onstrating flexibility of thinly plated interrays. Paratype ROM 44316, x 3.0. 18. Longitudinal cross-section through column and proximal portion of cup. One basal and part of adjoining radial are visible. Proximal nodals are transversely biconcave with slightly thickened epifacets. Internodals are typically transversely biconvex. See Text-Fig. 7A,B for diagrams of two noditaxes indicated here by pairs of arrows. Paratype ROM 44319, x 3.0. 19. Proximal AB-interray area enclosed by basals and lateral projections of t-shaped radials. Numerous irregular, polygonal interbrachials are visible. See Text-Fig. 5 for a diagram of this specimen. Paratype ROM 44310b, x 10.0. 20. Isolated radial showing characteristic lateral projections and deep ventral groove. Left projection is incomplete. Paratype ROM 44323, x 5.0. 21. Transverse cross-section through three calyces, each sectioned near bifurcation of rays. Fixed brachials contain prominent ventral groove. Paratype ROM 44313, x 3.0. PLATE 2, figs. 1-12. Stipatocrinus hulveri gen. et sp. nov. Reynales Formation, Rochester, New York. Blackened specimens whitened with ammonium chloride. 1. CD-interray of holotype specimen. Suboval interbrachial area in CD-interray, bounded by a single basal and t-shaped radials of C- and D-rays, is smaller than adjacent area in DE-interray, bounded below by two basals. See also Text-Fig. 6; Pl. 1, figs. 14,10. Rom 44310a, X 3.5. 2. Lateral view of nearly complete crown centred on B-ray. See also Pl. 2, fig. 12. Paratype Rom 4431 1d, x We). 3. Crown centred on B-ray. Suboval interbrachial area of proximal AB-interray is larger than adjacent suboval area in BC-interray. See also Text-Fig. 5; Pl. 1, figs. 6,19. Paratype Rom 44310b, x 2.8. 4. Partial crown centred on C-ray. Proximal bifurcation of C-ray ridge continues on basals. See also PI. 2, fig. 12. Paratype RoM 44311b, x 2.8. 5. CD-interray view of crown with most of column. See also PI. 2, fig. 12. Paratype RoM 4431le, x 2.0. 6. Pluricolumnal. Two internodals are attached to nodal with prominent epifacet. Paratype ROM 44318b, x 710: 7. Pluricolumnal. Internodal is attached to nodal displaying broad epifacet. Note small lumen. Paratype ROM 44317a, X 7.0. 8. Incomplete column coiled distally. Paratype RoM 44314, x 2.0. 9. CD-interray of individual with proximal portion of anal tube. See also Pl. 2, fig. 12. Paratype ROM 443lla, x 3.0. 10. Small slab with nearly complete crown and column near centre of photograph, two additional partial crowns and numerous pluricolumnals. These small specimens represent juvenile crinoids. Paratypes ROM 44312a—c, X 0.8. 11. Detail of above slab. Lower crown possesses two essentially complete arms. Paratypes ROM 44312a-c, x 1.6. 12. Well-preserved crinoids on small slab. Specimens are oriented subparallel to each other, suggesting unidirectional current at time of burial. Paratypes RoM 4431 la—-i, x 0.8. wv i v7 ISBN 0-88854-336-0 ISSN 0384-8159