Iocrinid Crinoids from the Ordovician of the Baltic Region, Estonia

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1 ISSN 00-00, Paleontological Journal, 05, Vol. 49, No., pp Pleiades Publishing, Ltd., 05. Original Russian Text W.I. Ausich, S.V. Rozhnov, T.W. Kammer, 05, published in Paleontologicheskii Zhurnal, 05, No., pp Iocrinid Crinoids from the Ordovician of the Baltic Region, Estonia W. I. Ausich a, S. V. Rozhnov b, and T. W. Kammer c a School of Earth Sciences, Ohio State University, 55 South Oval Mall, Columbus, OH 40, United States ausich.@osu.edu b Borissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya ul., Moscow, 7997 Russia rozhnov@paleo.ru c Department of Geology and Geography, West Virginia University Morgantown, WV 6506 USA tkammer@wvu.edu Received July 9, 04 Abstract A new crinoid species, Ristnacrinus oepiki sp. nov., from the Upper Ordovician (Katian Stage, Keila Regional Stage) of northern Estonia (Vasalemma) is described. The morphology and taxonomic position of the genus Ristnacrinus are discussed. Ristnacrinus previously referred to eustenocrinids based on the presence of compound radials in each of five rays is transferred to the Iocrinidae, because in a new interpretation, only one ray (C) has a superradial plate. At present, nine genera from the Early Ordovician to Early Silurian are included in the family Iocrinidae. In addition, Schaldichocrinus Rozhnov, 997 is designated as the correct spelling of the replacement name for Pariocrinus Rozhnov, 988 (non Eckert, 984) Keywords: Disparid, crinoids, Ordovician, Baltic DOI: 0.4/S INTRODUCTION Beyrich (879), Jaekel (90, 98), and Öpik (95, 94) were the first to describe a unique crinoid fauna from the Ordovician of the Baltic Region, which is presently considered as the Baltica paleocontinent. This work was continued mostly by Arendt (96, 965, 007) and Rozhnov (988, 990, 007), who described additional endemic taxa, confirming the fact that other Ordovician paleocontinents had their own distinctive faunas, for example, Gondwana (Ubaghs, 969, 98; Le Menn and Spjeldnaes, 996; Ausich et al., 00, 007; Lefebvre et al., 0). Ristnacrinus Öpik, 94 is one of these crinoids known for a long time exclusively from Baltica. During the 950s and 960s, a limited, but lively discussion ensued pertaining to the interpretation of plate homologies in the cup of this presumably very unusual crinoid (Yakovlev, 956; Moore, 96; Arendt, 96, 965). However, the Eustenocrinidae interpretation offered by Moore (96) was followed in the Treatise on Invertebrate Paleontology (Moore and Lane, 978) and the taxonomic position of Ristnacrinus has received no further attention. In the present study, the specimens investigated by Yakovlev (956) are reexamined and new specimens collected by Rozhnov are added. The new material comes from the Vasalemma Formation in the vicinity of the village of Vasalemma near the town of Keila, northern Estonia. This formation has been dated from the upper part of the Keila Regional Stage to Oandu Time and correlated with the bottom of the Katian Stage of the Upper Ordovician (Kröger et al., 04). The specimens come from the Keila part of the formation. Based on this material, a new species is described and the plate homology scheme proposed by Arendt (96, 965) is supported herein. According to these homologies, Ristnacrinus is transferred to the family Iocrinidae. Ristnacrinus has distinctive columnals with an unusual transverse ridge on the articular surface. Based on the assumption that this is a unique character of the genus, the geographical range of the genus, as now recognized, extends far beyond the Baltic Region. In addition, distinctive features of all known genera of the family Iocrinidae are listed (Table ) and Schaldichocrinus Rozhnov, 997 is designated as the correct spelling of the replacement name for Pariocrinus Rozhnov, 988 (non Eckert, 984). In the present study, we use the previously developed terminology (Moore, 96; Ubaghs, 978; Ausich et al., 999) and classification of crinoids proposed by Ausich (998). All specimens are housed in the Borissiak Paleontological Institute of the Russian Academy of Sciences, Moscow (PIN). All measurements are in mm; the asterisk sign (*) indicates that the respective specimen is incomplete or compressed. 45

2 46 AUSICH et al. Table. Comparison of Iocrinidae genera Genus Basal plates, lateral view Anal sac Number of primibrachials Number of arm branches Interradial plates Columnal outline Columnal construction Columnal facet in mesistele Iocrinus Hall, 866 Visible Large, plicate plates Several 8 Absent Pentalobate Holomeric Petaloid Caleidocrinus (Caleidocrinus) Waagen et Jahn, 899 Invisible Unknown More than 4 Present Pentagonal to circular Holomeric Synarthry Caleidocrinus (Huxleycrinus) Donovan, 985 Visible Unknown At least Present Pentagonal Holomeric Unknown Margoiocrinus Donovan in Donovan et al., 0 Visible Unknown 7 4 Absent Pentagonal to circular Holomeric Petaloid or smooth Pariocrinus Eckert, 984 (non Rozhnov, 988) Visible Smooth plates 4 or 5 At least Absent Circular to pentagonal Pentameric Unknown Peltacrinus Warn, 98 Visible Unknown From to 4 At least 4 Absent Pentalobate Pentameric Unknown Schaldichocrinus Rozhnov, 997 Visible Unknown 4 Absent Circular Pentameric Radial symplexy Ristnacrinus Öpik, 94 Invisible Unknown or 4 Absent Elliptical Holomeric Synarthry Tornatilicrinus Guensburg, 984 Visible Smooth plates From 7 to 9 Absent Pentagonal Pentameric Petaloid Westheadocrinus Donovan, 989 Visible Plates smooth 4 Absent Pentagonal Holomeric Radial symplexy PALEONTOLOGICAL JOURNAL Vol. 49 No. 05

3 IOCRINID CRINOIDS FROM THE ORDOVICIAN OF THE BALTIC REGION, ESTONIA 47 SYSTEMATIC PALEONTOLOGY CLASS CRINOIDEA SUBCLASS DISPARIDA Order Myelodactylidae Family Iocrinidae Moore et Laudon, 94 Genus Ristnacrinus Öpik, 94 Type species. Ristnacrinus marinus Öpik, 94 from the Upper Ordovician of Estonia (Sandbian Stage, Jõhvi Regional Stage) D i a g n o s i s. Basal plates not visible in lateral view (characteristics of anal sac not known); one or two primibrachials, arms branching four times, interray plates absent (fixed plates between adjacent rays), columnal outlines elliptical, stem holomeric, articular facets of columnals synarthrial. Species composition. In addition to the type species, the only other certain species is R. oepiki sp. nov. described below (Ristnacrinus species established on columnals alone are excluded from consideration). Crowns and cups of Ristnacrinus are only known from the Upper Ordovician (Sandbian and Katian Stages) of Estonia as a part of the Baltic paleocontinent (note that R.? altobasalis Brower et Venius, 974 does not belong to Ristnacrinus). Nevertheless, one of the most prominent distinctive characters of the genus is the elliptically shaped columnals, with a fulcral ridge. Similar columnals were referred to the genus Ristnacrinus and recorded in Algeria, Estonia, France, Kazakhstan, Latvia, Lithuania, Russia, Sardinia, Spain, Sweden, Great Britain, Uzbekistan, and Mongolia (see Webster, 00; Rozhnov et al., 009). Comparison. Ristnacrinus is compared with other Iocrinidae in Table. Remarks. As noted by Öpik (94), Ristnacrinus is unusual in the arrangement of plates; all plates of the aboral cup are aligned vertically in a radial orientation. Öpik (94) considered the lowermost visible circlet to be the radial circlet, although he suggested that it could have been composed of either the infrabasal or subradial plates (Öpik terminology). In a letter from F. Bather (quoted in Öpik, 94, pp. 5 7), Bather suggested that the basal circlet was lost and that the two lower circlets were inferradials below and superradials above. It should also be noted that the Öpik (94, text-fig. ) plate interpretation had the rays mislabeled (compare with Fig. herein). Yakovlev (956, text-fig. ) illustrated a specimen with one of the lower circlets of plates missing. This specimen clearly has a plate circlet concealed within a basal concavity. Further, this circlet has at least one suture, indicating that this is a multiplated circlet that is not a columnal (Ristnacrinus columnals are holomeric). Yakovlev (956) interpreted the C and E rays to have simple radials, with brachial plates arranged in a vertical row above them. This follows from designations of these plates in the figure which he took from the paper by Öpik, using his incorrectly designated E D X Fig.. Plate diagram for the cup of Ristnacrinus oepiki sp. nov. Designations: radial and superradial plates are black, inferradial is covered with horizontal lines; (X) anal X; basal circlet is shown as a circle of five sectors with pentalobate axial canal in the center. C rays. According to the designations of plates provided by Yakovlev, the anal plate X and other anal plates located on its continuation leaned on the left shoulder of the first brachial plate. It remains uncertain whether or not Moore (96, p. 5) was aware of Yakovlev (956); however, Moore adamantly argued that the interpretation of Öpik (94) was incorrect and he supported the interpretation of Bather (in Öpik, 94). Thus, Moore (96) regarded Ristnacrinus as a crinoid with five lower (inferradials) and five upper radials (superradials) and, consequently, he placed this genus in the Eustenocrinidae. With his own plate interpretation, Moore (96, text-fig..) essentially repeated Öpik's (94) plate diagram, but he also added a basal circlet for which he presented no evidence. Arendt (96, 965) argued for an iocrinid interpretation of the morphology of this genus, referring to the photographs provided by Yakovlev (956) and Öpik (94). Regardless, without further discussion, Moore s (96) interpretation was followed in Moore and Lane (978, text-figs. 48.a, 48.b). Moreover, Moore and Lane (978) suggested that the basal circlet was fused with the proximal columnal or absent, which contrasts with Yakovlev s illustration. The well-pronounced sutures and distal inferradial (sensu Moore, 96) facet with a fulcral ridge and aboral ligament fossa bring the Eustenocrinidae interpretation into question, as argued by Arendt (96, 965). Compound radial plates are a part of the aboral cup (Sevastopulo and Lane, 988), and inferradials and superradials are typically sutured securely to one another as well as to plates of adjacent rays. In the new material of R. oepiki stored at PIN, it is clear that superradials (interpreted here as primibrachials) were not laterally sutured (Fig. ), and the articulation B A PALEONTOLOGICAL JOURNAL Vol. 49 No. 05

4 48 AUSICH et al. 5 mm mm Fig.. Ristnacrinus oepiki sp. nov., specimen PIN, no. 45/908, lateral view, ray (photograph) and drawings of the basal view of calyx with the basal plates covered by the proximal columnal (lower) and at the level of basal plates 0.4 mm deeper than the previous view. Radial plates and axial canal are black. mm between the inferradial and superradial (interpretive here as the radial and first primibrachial) has a large fulcral ridge that allowed considerable movement (Pl. 7, figs., 5), which is typical for a radial first primibrachial articulation. As illustrated by Yakovlev (956) and argued by Arendt (96, 965), Ristnacrinus has a basal circlet and it is not fused with the proximal columnal, as Moore and Lane (978) assumed. The basal circlet is completely hidden in the basal concavity and is only visible on a specimen with a radial plate missing (Figs., ; Pl. 7, fig. 6). The Ristnacrinus plate diagram of Öpik shows that a ray that he interpreted as the E is distinguished from others by the fact that the third primibrachial (instead of the second, as in other rays) is axillary. In addition, there are two further remarks. First, as noted above, rays in the study by Öpik were mislabeled; the E ray after Öpik is actually ray A. Second, in the majority of new specimens, the number of primibrachials is constant in most of the rays and the second primibrachial is typically axillary. In four specimens (PIN, nos. 45/905, 45/906, 45/907 and 45/88), the A ray has three primibrachials. In the last specimen (PIN, no. 45/88), the C ray contains only one primibrachial (just above the upper radial), whereas three other rays (B, D, and E) have two brachials each. We believe that Ristnacrinus has simple radial plates in the A, B, D, and E rays and only in the C ray, it is compound; thus, this genus should be assigned to the Iocrinidae, as proposed by Arendt (96, 965). At present, the family Iocrinidae includes nine genera: Iocrinus Hall, 866; Caleidocrinus (Caleidocrinus) Waagen et Jahn, 899; Caleidocrinus (Huxleycrinus) Donovan, 985; Margoiocrinus Donovan in Donovan et al., 0; Peltacrinus Warn, 98, Schaldichocrinus Rozhnov, 997; Ristnacrinus Öpik, 94; Tornatilicrinus Guensburg, 984; and Westheadocrinus Donovan, 989. Members of these genera range in age from the Dapingian or Darriwilian (Middle Ordovician) to Rhuddanian (Early Silurian) and are known from the following paleocontinents: Avalonia, Baltica, eastern and western Gondwana, and Laurentia. Iocrinid genera are distinguished by their small size (whether or not the basal circlet is visible in lateral view of the aboral cup), by the anal sac, the number of primibrachials, the number of arm branching within a ray, the presence or absence of interradial plates, the shape of columnals, columnal construction, and the articulation type on the columnals. Ristnacrinus oepiki Ausich, Rozhnov et Kammer, sp. nov. Plate 7, figs. 7 E t y m o l o g y. In honor of the Estonian paleontologist A. Öpik. H o l o t y p e. PIN, no. 45/90, crown with a short stem fragment; Estonia, quarry near the village of Vasalemma; Upper Ordovician, lower part of the Katian Stage, Keila Regional Stage, Vasalemma Formation. D e s c r i p t i o n (Figs., ). The radial plates are wider than high, with more pronounced concavity on the distal sutures of primaxils, only a faint fulcral ridge on the columnals, and short proximal primary nodals, with a small prominence of the lateral sides. The aboral cup is medium cone in outline; the width-to-height ratio is approximately.; the plates are moderately convex, with a smooth surface. The basal circlet is not Explanation of Plate 7 Figs. 7. Ristnacrinus oepiki sp. nov.: () specimen PIN, no. 45/90, crown with proximal stem part: (a) ray C, lateral view, (b) ray E, lateral view; () holotype PIN, no. 45/90, crown with proximal stem part: (a) ray E, lateral view, (b) interray BC, lateral view; () specimen PIN, no. 45/90, crown with proximal stem part: (a) ray E, lateral view, (b) interray BC, lateral view; (4) specimen PIN, no. 45/904, crown with proximal stem part: (4a) interray BC, lateral view, (4b) ray E, lateral view; (5) specimen PIN, no. 45/907, crown with proximal stem part: (5a) ray E, lateral view, (5b) interray BC, lateral view; (6) specimen PIN, no. 45/906, crown with proximal stem part: (6a) ray C, lateral view (C plate is absent and the disk of basal plates is visible), (6b) ray A, lateral view; (7) specimen PIN, no. 45/905, crown with proximal stem part: (7a) ray E, lateral view, (7b) interray BC, lateral view, (7c) view from below; northern Estonia, limestone quarry near the village of Vasalemma; Upper Ordovician, Katian Stage, Keila Regional Stage. Scale bars: (7c) mm; others, 9 mm. PALEONTOLOGICAL JOURNAL Vol. 49 No. 05

5 IOCRINID CRINOIDS FROM THE ORDOVICIAN OF THE BALTIC REGION, ESTONIA Plate 7 a b а b 4b 4а а b 6а 5а 5b 7c 7а PALEONTOLOGICAL JOURNAL 7b Vol. 49 No. 05 6b 49

6 50 AUSICH et al. visible in lateral view, but with a radial plate missing from the cup, it is visible in a shallow (0.5 mm deep) depression and completely covered by the proximal columnal. Five basal plates approximately identical in shape and size form the disk bordering the cup cavity. In the center of the disk formed by five basal plates, there is a five-lobed lumen of the axial canal. The lobes of the axial canal are positioned opposite the sutures between radial plates, i.e., interradially. The axial canal is approximately 0.9 mm in diameter, i.e., approximately one-third of the basal circlet diameter. The radial circlet is 00% of the aboral cup height; the A, B, D, and E radial plates are simple; the C radial is compound; the simple radials are slightly higher than wide; the C inferradial is tetragonal, slightly wider than high; the C superradial is pentagonal, wider than high. The articulation of the anal X is on a small facet of the upper left shoulder of the C superradial; the C arm articulates to a wide right shoulder of the C superradial. The C inferradial is slightly smaller than the simple radial plates of the A, B, D, and E rays. The C superradial is in line with, but slightly smaller than, the first primibrachial of the A, B, D, and E rays. The facets between the A, B, D, and E radials and superjacent first primibrachials are gaping, planate; the fulcral ridge extends throughout the facet width; the aboral ligament fossa is located in the middle part of the aboral margin of the facet. The anal X plate is located above the aboral cup, supported from below by the C superradial at a heterotomous division; it is tetragonal, approximately.6 times higher than wide. At least two more distal plates above the anal X are known; all are higher than wide. The anal sac is not preserved. The arms branch isotomously at least four times; the axillaries are not swollen; the number of brachials in the brachitaxis varies, with more brachials on the medial side of the axillary. The second primibrachials are axillary in the majority of rays. The primaxils are pentagonal, with straight sides. The secundibrachials are usually three, or less often, four or two. The number of tertibrachials varies from three to seven; among a total of secundibrachitaxes examined, one has three plates, nine have four, four have five, three have six, one has seven, and three additionally examined specimens have more than six plates. The proxistele columnals are heteromorphic, N---, circular, holomeric; the nodals are five times wider than high; facets lack distinctive features; the lateral margins are convex; the internodals are extremely thin; the lumen is pentalobate, 0% of the nodal diameter. The proxistele is approximately 0 mm high. The mesistele columnals are heteromorphic, N-, very slightly elliptical, holomeric; the nodals are. times wider than high; the facet has a synarthrial ridge, other distinctive features are absent. The lateral margins are convex; the lumen is pentalobate. Measurements, mm. Specimen PIN no. 45/ Diameter of cup base Maximum cup width Cup height Height of first primibrachial in C ray 90, holotype Va r i a b i l i t y. The collection examined displays variability in four successive arm branchings. Each axillary is isotomous, but the number of nonaxillary brachials may vary; therefore, in general, this arm branching is described here as poor isotomy. Arm branching tends slightly toward an exotomous pattern, but, again, each division is isotomous. The number of primibrachials is typically two, although four specimens have three in the A ray and one specimen has only one primibrachial in the C ray, which is located just above the superradial. The number of nonaxillaries vary in different brachitaxes (Table ). C o m p a r i s o n. The new species differs from R. marinus in the greater relative width of radial plates (which are approximately as wide as high, whereas in R. marinus, they are higher than wide); the greater convexity of the suture between the primaxils and the first secundibrachials; the weak fulcral ridge on columnals; and the short proximal primary nodals which, in addition, have less convex lateral margins. Remarks. Ristnacrinus was presumably described based on three specimens, only two of which were figured (Öpik, 94). There is inconsistency (plate numbers cited in the text versus plates and plate descriptions) with regard to which specimen should be the lectotype of R. marinus. We regard the nearly complete crown with a long column attached (Öpik, 94, pl., fig., pl., fig. ) as the lectotype and a poorly preserved aboral cup with proximal brachials and isolated columnals are additional specimens. Note that PALEONTOLOGICAL JOURNAL Vol. 49 No. 05

7 IOCRINID CRINOIDS FROM THE ORDOVICIAN OF THE BALTIC REGION, ESTONIA 5 Table. Brachial number variation in particular rays Specimen PIN, no. 45/ Brachitaxis 90 Primibrachials Quartibrachials 90, holotype Primibrachials Quartibrachials 90 Primibrachials Ray A B C D E Primibrachials 905 Primibrachials 906 Primibrachials 907 Primibrachials Quartibrachials Primibrachials 88 Primibrachials Quartibrachials Pentabrachials Hexabrachials to 7 4 to 7 Öpik (94) indicated in the figure caption that the poorly preserved aboral cup had defective basals. Moore and Lane (978, text-fig. 48.a, 48.b) republished Öpik's illustration. M a t e r i a l. Eight specimens from the type locality. Genus Schaldichocrinus Rozhnov, 997 Pariocrinus (non Eckert, 984): Rozhnov, 988, p. 76. Schaldichocrinus: Rozhnov, 997a, p. 94 (nom. substit.). Shaldikhocrinus: Rozhnov, 997a, p. 94 (nom. null.). Scheldickocrinus: Rozhnov, 997b, p. 47 (nomen. null.). Type species. Schaldichocrinus ladogensis (Rozhnov, 988) [nom. substit. pro Pariocrinus ladogensis Rozhnov, 988]; Darriwilian of the eastern Leningrad oblast. D i a g n o s i s. Basal plates visible in lateral view, characteristics of anal sac not known; three primibrachials, four divisions of each arm, interradial plates absent, columnal outlines circular, each columnal composed of pentameres, columnal articular facet symplexial. Species composition. Type species. R e m a r k s. Rozhnov (997a) recognized that Pariocrinus Eckert, 984 and Pariocrinus Rozhnov, 988 are homonyms and the former has priority. Rozhnov (997a) proposed Schaldichocrinus as a replacement name for Pariocrinus Rozhnov, 988, but errors added further confusion to this change. Schaldichocrinus Rozhnov, 997 is designated herein as the correct replacement name, and Shaldikhocrinus (Rozhnov, 997a) and Scheldickocrinus (Rozhnov, 997b) are designated nomen nullum. The type species is Schaldichocrinus ladogensis (Rozhnov, 988) and the holotype is specimen PIN, no. 45/4 of the Volkhov Regional Stage (Darriwilian) of the eastern Leningrad oblast. ACKNOWLEDGMENTS This publication was partially supported by the National Science Foundation collaborative project Assembling Echinoderm Tree of Life, project nos (Ohio State University) and 0656 (West Virginia University), by the Russian Foundation for Basic Research (project no ) and the PALEONTOLOGICAL JOURNAL Vol. 49 No. 05

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Aude), Courtessole, R., Marek, L., Pillet, J., et al., Eds., Carcassonne, 98, pp. 55. Webster, G.D., Bibliography and Index of Paleozoic Crinoids, Coronates, and Hemistreptocrinoids, Pap. Geol. Soc. Am. Spec., 00, no. 6, pp. 5. [ crinoid.gsajournals.org/crinoidmod]. Yakovlev, N.N., On the revision of characteristics of the genus Ristnacrinus Öpik, Ezhegodn. Vsesoyuzn. Paleontol. Ob-va, 956, no. 5, pp Translated by G. Rautian SPELL:. ok PALEONTOLOGICAL JOURNAL Vol. 49 No. 05