ISSN 00310301, Paleontological Journal, 2015, Vol. 49, No. 2, pp. 145–152. © Pleiades Publishing, Ltd., 2015. Original Russian Text © W.I. Ausich, S.V. Rozhnov, T.W. Kammer, 2015, published in Paleontologicheskii Zhurnal, 2015, No. 2, pp. 36–43.
Iocrinid Crinoids from the Ordovician of the Baltic Region, Estonia W. I. Ausicha, S. V. Rozhnovb, and T. W. Kammerc a
School of Earth Sciences, Ohio State University, 155 South Oval Mall, Columbus, OH 43210, United States email:
[email protected] bBorissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya ul. 123, Moscow, 117997 Russia email:
[email protected] c Department of Geology and Geography, West Virginia University Morgantown, WV 26506 USA email:
[email protected] Received July 29, 2014
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 posi tion 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 interpre tation, 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, 1997 is designated as the correct spelling of the replacement name for Pariocrinus Rozhnov, 1988 (non Eckert, 1984). Keywords: Disparid, crinoids, Ordovician, Baltic DOI: 10.1134/S0031030115020069
INTRODUCTION Beyrich (1879), Jaekel (1902, 1918), and Öpik (1925, 1934) 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 (1963, 1965, 2007) and Rozhnov (1988, 1990, 2007), who described additional endemic taxa, confirming the fact that other Ordovician paleocontinents had their own distinctive faunas, for example, Gondwana (Ubaghs, 1969, 1983; Le Menn and Spjeldnaes, 1996; Ausich et al., 2002, 2007; Lefebvre et al., 2013). Rist nacrinus Öpik, 1934 is one of these crinoids known for a long time exclusively from Baltica. During the 1950s and 1960s, a limited, but lively discussion ensued per taining to the interpretation of plate homologies in the cup of this presumably very unusual crinoid (Yakovlev, 1956; Moore, 1962; Arendt, 1963, 1965). However, the Eustenocrinidae interpretation offered by Moore (1962) was followed in the Treatise on Invertebrate Paleontology (Moore and Lane, 1978) and the taxo nomic position of Ristnacrinus has received no further attention. In the present study, the specimens investigated by Yakovlev (1956) 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., 2014). The specimens come from the Keila part of the forma tion. Based on this material, a new species is described and the plate homology scheme proposed by Arendt (1963, 1965) 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 1) and Schaldi chocrinus Rozhnov, 1997 is designated as the correct spelling of the replacement name for Pariocrinus Rozhnov, 1988 (non Eckert, 1984). In the present study, we use the previously devel oped terminology (Moore, 1962; Ubaghs, 1978; Ausich et al., 1999) and classification of crinoids pro posed by Ausich (1998). All specimens are housed in the Borissiak Paleontological Institute of the Russian Academy of Sciences, Moscow (PIN). All measure ments are in mm; the asterisk sign (*) indicates that the respective specimen is incomplete or compressed.
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Visible
Westheadocrinus Donovan, 1989
Invisible
Ristnacrinus Öpik, 1934
Visible
Visible
Schaldichocrinus Rozhnov, 1997
Tornatilicrinus Guensburg, 1984
Visible
Peltacrinus Warn, 1982
Unknown
Visible Margoiocrinus Donovan in Donovan et al., 2011
No. 2
Plates smooth
Smooth plates
Unknown
Unknown
Unknown
Smooth plates
Unknown
Visible
Caleidocrinus (Huxleycrinus) Donovan, 1985
Visible
Unknown
Invisible
Caleidocrinus (Caleidocrinus) Waagen et Jahn, 1899
Pariocrinus Eckert, 1984 (non Rozhnov, 1988)
Large, pli cate plates
Anal sac
Visible
Basal plates, lateral view
Iocrinus Hall, 1866
Genus
Table 1. Comparison of Iocrinidae genera
3
From 7 to 9
1 or 2
3
From 2 to 4
4 or 5
7
2
2
Several
4
1
4
4
At least 4
At least 3
4
At least 3
More than 4
8
Number Number of primibrachials of arm branches
Absent
Absent
Absent
Absent
Absent
Absent
Absent
Present
Present
Absent
Interradial plates
Pentagonal
Pentagonal
Elliptical
Circular
Pentalobate
Circular to pentagonal
Pentagonal to circular
Pentagonal
Pentagonal to circular
Pentalobate
Columnal outline
Holomeric
Pentameric
Holomeric
Pentameric
Pentameric
Pentameric
Holomeric
Holomeric
Holomeric
Holomeric
Columnal construction
Radial symplexy
Petaloid
Synarthry
Radial symplexy
Unknown
Unknown
Petaloid or smooth
Unknown
Synarthry
Petaloid
Columnal facet in mesistele
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SYSTEMATIC PALEONTOLOGY
C
CLASS CRINOIDEA SUBCLASS DISPARIDA Order Myelodactylidae Family Iocrinidae Moore et Laudon, 1943 Genus Ristnacrinus Öpik, 1934
E
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B
A
X
Ty p e s p e c i e s. Ristnacrinus marinus Öpik, 1934 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, inter ray plates absent (fixed plates between adjacent rays), columnal outlines elliptical, stem holomeric, articular facets of columnals synarthrial. S p e c i e s c o m p o s i t i o n. In addition to the type species, the only other certain species is R. oepiki sp. nov. described below (Ristnacrinus species estab lished on columnals alone are excluded from consid eration). Crowns and cups of Ristnacrinus are only known from the Upper Ordovician (Sandbian and Katian Stages) of Estonia as a part of the Baltic paleo continent (note that R.? altobasalis Brower et Venius, 1974 does not belong to Ristnacrinus). Nevertheless, one of the most prominent distinctive characters of the genus is the elliptically shaped columnals, with a ful cral ridge. Similar columnals were referred to the genus Ristnacrinus and recorded in Algeria, Estonia, France, Kazakhstan, Latvia, Lithuania, Russia, Sar dinia, Spain, Sweden, Great Britain, Uzbekistan, and Mongolia (see Webster, 2003; Rozhnov et al., 2009). C o m p a r i s o n. Ristnacrinus is compared with other Iocrinidae in Table 1. R e m a r k s. As noted by Öpik (1934), Ristnacrinus is unusual in the arrangement of plates; all plates of the aboral cup are aligned vertically in a radial orientation. Öpik (1934) 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, 1934, pp. 5–7), Bather suggested that the basal circlet was lost and that the two lower circlets were inferradials below and superra dials above. It should also be noted that the Öpik (1934, textfig. 1) plate interpretation had the rays mislabeled (compare with Fig. 1 herein). Yakovlev (1956, textfig. 1) 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 holom eric). Yakovlev (1956) interpreted the C and E rays to have simple radials, with brachial plates arranged in a vertical row above them. This follows from designa tions of these plates in the figure which he took from the paper by Öpik, using his incorrectly designated PALEONTOLOGICAL JOURNAL
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Fig. 1. 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 penta lobate axial canal in the center.
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 (1962, p. 35) was aware of Yakovlev (1956); however, Moore adamantly argued that the interpretation of Öpik (1934) was incorrect and he supported the interpreta tion of Bather (in Öpik, 1934). Thus, Moore (1962) regarded Ristnacrinus as a crinoid with five lower (inferradials) and five upper radials (superradials) and, consequently, he placed this genus in the Eustenocrin idae. With his own plate interpretation, Moore (1962, textfig. 2.1) essentially repeated Öpik's (1934) plate diagram, but he also added a basal circlet for which he presented no evidence. Arendt (1963, 1965) argued for an iocrinid inter pretation of the morphology of this genus, referring to the photographs provided by Yakovlev (1956) and Öpik (1934). Regardless, without further discussion, Moore’s (1962) interpretation was followed in Moore and Lane (1978, textfigs. 348.1a, 348.1b). Moreover, Moore and Lane (1978) suggested that the basal circlet was fused with the proximal columnal or absent, which contrasts with Yakovlev’s illustration. The wellpronounced sutures and distal inferradial (sensu Moore, 1962) facet with a fulcral ridge and abo ral ligament fossa bring the Eustenocrinidae interpre tation into question, as argued by Arendt (1963, 1965). Compound radial plates are a part of the aboral cup (Sevastopulo and Lane, 1988), 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. 1), and the articulation
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1 mm
1 mm
5 mm
Fig. 2. Ristnacrinus oepiki sp. nov., specimen PIN, no. 4125/908, lateral view (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.
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. 1, 5), which is typical for a radial–first primibrachial articulation. As illustrated by Yakovlev (1956) and argued by Arendt (1963, 1965), Ristnacrinus has a basal circlet and it is not fused with the proximal columnal, as Moore and Lane (1978) assumed. The basal circlet is completely hidden in the basal concavity and is only visible on a specimen with a radial plate missing (Figs. 1, 2; 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 con stant in most of the rays and the second primibrachial
is typically axillary. In four specimens (PIN, nos. 4125/905, 4125/906, 4125/907 and 4125/882), the A ray has three primibrachials. In the last specimen (PIN, no. 4125/882), 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 com pound; thus, this genus should be assigned to the Ioc rinidae, as proposed by Arendt (1963, 1965). At present, the family Iocrinidae includes nine genera: Iocrinus Hall, 1866; Caleidocrinus (Caleidocri nus) Waagen et Jahn, 1899; Caleidocrinus (Huxleycri nus) Donovan, 1985; Margoiocrinus Donovan in Donovan et al., 2011; Peltacrinus Warn, 1982, Schaldi chocrinus Rozhnov, 1997; Ristnacrinus Öpik, 1934; Tornatilicrinus Guensburg, 1984; and Westheadocrinus Donovan, 1989. Members of these genera range in age from the Dapingian or Darriwilian (Middle Ordovi cian) to Rhuddanian (Early Silurian) and are known from the following paleocontinents: Avalonia, Baltica, eastern and western Gondwana, and Laurentia. Ioc rinid 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. 1–7
E t y m o l o g y. In honor of the Estonian paleon tologist A. Öpik. H o l o t y p e. PIN, no. 4125/902, 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 For mation. D e s c r i p t i o n (Figs. 1, 2). 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 abo ral cup is medium cone in outline; the widthtoheight ratio is approximately 1.2; the plates are moderately convex, with a smooth surface. The basal circlet is not
Explanation of Plate 7 Figs. 1–7. Ristnacrinus oepiki sp. nov.: (1) specimen PIN, no. 4125/901, crown with proximal stem part: (1a) ray C, lateral view, (1b) ray E, lateral view; (2) holotype PIN, no. 4125/902, crown with proximal stem part: (2a) ray E, lateral view, (2b) interray BC, lateral view; (3) specimen PIN, no. 4125/903, crown with proximal stem part: (3a) ray E, lateral view, (3b) interray BC, lateral view; (4) specimen PIN, no. 4125/904, crown with proximal stem part: (4a) interray BC, lateral view, (4b) ray E, lateral view; (5) specimen PIN, no. 4125/907, crown with proximal stem part: (5a) ray E, lateral view, (5b) interray BC, lateral view; (6) spec imen PIN, no. 4125/906, 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. 4125/905, 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) 3 mm; others, 9 mm. PALEONTOLOGICAL JOURNAL
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IOCRINID CRINOIDS FROM THE ORDOVICIAN OF THE BALTIC REGION, ESTONIA Plate 7 2a
1b
1а
2b
4b
4а 3а
3b
6а 5а
5b
7c
7а
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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 fivelobed 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 onethird of the basal circlet diameter. The radial circlet is 100% 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 super radial. 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 fac ets 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 abo ral margin of the facet.
The anal X plate is located above the aboral cup, supported from below by the C superradial at a hetero tomous division; it is tetragonal, approximately 1.6 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 num ber of tertibrachials varies from three to seven; among a total of 22 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, N121, 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, 20% of the nodal diameter. The proxistele is approximately 10 mm high. The mesistele columnals are heteromor phic, N1, very slightly elliptical, holomeric; the nodals are 3.3 times wider than high; the facet has a synarthrial ridge, other distinctive features are absent. The lateral margins are convex; the lumen is pentalobate.
M e a s u r e m e n t s , m m: Specimen PIN no. 4125/
Diameter of cup base
Maximum cup width
Cup height
Height of first primibrachial in C ray
902, holotype
5.0
6.5
2.6
1.9
903
4.1
6.1
2.5
1.5
904
4.5
6.5
2.6
1.6
905
4.1
6.0
2.2
1.5
906
4.0
5.1
3.1
1.8
907
4.0
6.0
2.4
1.5
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 speci mens 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 nonaxillar ies vary in different brachitaxes (Table 2). 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. R e m a r k s. Ristnacrinus was presumably described based on three specimens, only two of which were figured (Öpik, 1934). 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 com plete crown with a long column attached (Öpik, 1934, pl. 1, fig. 1, pl. 2, fig. 1) as the lectotype and a poorly preserved aboral cup with proximal brachials and iso lated columnals are additional specimens. Note that PALEONTOLOGICAL JOURNAL
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Table 2. Brachial number variation in particular rays Specimen PIN, no. 4125/
Ray Brachitaxis A
B
C
D
E
2 333
2
2 33 444 55
901
Primibrachials Secundibrachials Tertibrachials Quartibrachials
2
2 33 45
902, holotype
Primibrachials Secundibrachials Tertibrachials Quartibrachials
2 3–4 6–5 6+ 6+ 4
2 33 4643 556
903
Primibrachials Secundibrachials Tertibrachials
2
2 33 4 5 6+ 4
2 33 4754
2 33 4754
904
Primibrachials
3
2
3
2
2
905
Primibrachials
3
2
2
2
2
906
Primibrachials Secundibrachials
2 4
2 3
2 3
2 3
2 3
907
Primibrachials Secundibrachials Tertibrachials Quartibrachials
3 3
2 3
2 4
2 3
2 2
908
Primibrachials
3
3
2
2
2
882
Primibrachials Secundibrachials Tertibrachials Quartibrachials Pentabrachials Hexabrachials
3 3 5 6
2 23 37 47 5 6
1 43 457 5
2 3 3553 to 7
2 3 4 to 7
Öpik (1934) indicated in the figure caption that the poorly preserved aboral cup had “defective basals.” Moore and Lane (1978, textfig. 348.1a, 348.1b) republished Öpik's illustration. M a t e r i a l. Eight specimens from the type locality. Genus Schaldichocrinus Rozhnov, 1997 Pariocrinus (non Eckert, 1984): Rozhnov, 1988, p. 76. Schaldichocrinus: Rozhnov, 1997a, p. 94 (nom. substit.). Shaldikhocrinus: Rozhnov, 1997a, p. 94 (nom. null.). Scheldickocrinus: Rozhnov, 1997b, p. 437 (nomen. null.).
Ty p e s p e c i e s. Schaldichocrinus ladogensis (Rozhnov, 1988) [nom. substit. pro Pariocrinus ladogensis Rozhnov, 1988]; 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 primibra chials, four divisions of each arm, interradial plates absent, columnal outlines circular, each columnal composed of pentameres, columnal articular facet symplexial. S p e c i e s c o m p o s i t i o n. Type species. PALEONTOLOGICAL JOURNAL
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R e m a r k s. Rozhnov (1997a) recognized that Pariocrinus Eckert, 1984 and Pariocrinus Rozhnov, 1988 are homonyms and the former has priority. Rozhnov (1997a) proposed Schaldichocrinus as a replacement name for Pariocrinus Rozhnov, 1988, but errors added further confusion to this change. Schaldi chocrinus Rozhnov, 1997 is designated herein as the correct replacement name, and Shaldikhocrinus (Rozhnov, 1997a) and Scheldickocrinus (Rozhnov, 1997b) are designated nomen nullum. The type spe cies is Schaldichocrinus ladogensis (Rozhnov, 1988) and the holotype is specimen PIN, no. 4125/4 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. 1036416 (Ohio State University) and 1036356 (West Virginia University), by the Russian Foundation for Basic Research (project no. 120401750) and the
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Translated by G. Rautian
PALEONTOLOGICAL JOURNAL
Vol. 49
No. 2
2015
