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A New Metazoan from the Vendian of the White Sea, Russia, with Possible Affinities to the Ascidians M

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A New Metazoan from the Vendian of the White Sea, Russia, with Possible Affinities to the Ascidians M ISSN 00310301, Paleontological Journal, 2012, Vol. 46, No. 1, pp. 1–11. © Pleiades Publishing, Ltd., 2012. Original Russian Text © M.A. Fedonkin, P. VickersRich, B.J. Swalla, P. Trusler, M. Hall, 2012, published in Paleontologicheskii Zhurnal, 2012, No. 1, pp. 3–14. A New Metazoan from the Vendian of the White Sea, Russia, with Possible Affinities to the Ascidians M. A. Fedonkina, b, c, P. VickersRicha, c, B. J. Swallad, P. Truslerc, and M. Hallc aBorissiak Paleontological Institute, Russian Academy of Science, Profsoyuznaya 123, Moscow, 117997 Russia bGeological Institute, Russian Academy of Sciences, Pyzhevsky per 7, Moscow, 119017 Russia cMonash University, Victoria 3800, Australia d238 Kincaid Hal, University of Washington, U.S.A email: [email protected] Received April 4, 2010 Abstract—Two specimens recovered from late Neoproterozoic shallow marine sediments of northern Russia may be the oldest known ascidians. Dated at around 555 Ma, these, together with the younger Ausia from the Nama Group in southwestern Africa, are probably relatives of these invertebrate chordates, which have a deep time origin predicted by molecular studies. Keywords: Ediacaran, Vendian, chordate ancestor, ascidian tunicates, Russia, Namibia. DOI: 10.1134/S0031030112010042 INTRODUCTION along these bands suggesting affinity to the suborder Phlebobranchia (order Enterogona). In 1985 Hahn and Pflug described two new Meta zoan genera Ausia and Kuibisia from the Neoprotero zoic Kuibis Quartzite in the Nama Group in Namibia. Family Ausiidae Hahn et Pflug, 1985 The specimens came from the Aus locality at Aar Genus Burykhia Fedonkin, VickersRich, Swalla, Farm, known to contain a rich variety of Neoprotero Trusler et Hall, gen. nov. zoic metazoan fossils. The fossils described were small in size. The visible length of an incomplete fragment of Etymology. In honor of Tatyana Andreevna the holotype of Ausia fenestrata was about 7.5 cm, and and Timofei Antonovich Burykh, citizens of the vil width was from 1.5 to 3 cm. lage of Syuzma who helped in the fieldwork. Rich collections of fossil softbodied metazoans Type species. Burykhia hunti sp. nov. were found during field excavations in the Vendian D i a g n o s i s. Depressions along bands (most beds of northern Russia, on the Syuzma River, Sum similar to longitudinal bands observed in modern mer Coast of the White Sea, to the west of Arkhangelsk Phlebobranchia); these depressions clearly separated (Fig. 1). Two specimens found in 1995 and 2003 are from each other by flat area almost equal in size to the similar in morphology to the only specimen of Ausia “depressions” or slightly larger. “Depressions” in from the Late Neoproterozoic Nama Group of bands arranged in rows at right angle to “longitudinal” Namibia. In this paper we describe new fossils from bands. Undistorted depressions elliptical in shape. Russia, discuss their possible affinity to the ascidian Longitudinal rounded ridges clearly visible; probably tunicates and make comparisons with other animal corresponding to grooves in living animal cavity. groups. “Longitudinal” bands converging in alternating order to form a zigzagshaped ridge apparently correspond ing to endostyle. Generally body saccular, apparently SYSTEMATIC PALEONTOLOGY singular rather than colonial. P h y l u m Chordata Species composition. Type species. S u b p h y l u m Urochordata Comparison. Burykhia is considerably larger than Ausia (Pl. 1, figs. 1–3). In Ausia the crests CLASS ASCIDIACEA between bands are not prominent, whereas they are Placement in the class Ascidiacea is based on the distinct in Burykhia; The “depressions” in Burykhia fact that the fossils have a similar saclike morphology are considerably wider, especially in specimen PIN, and regularly perforated bands resembling the gill bag no. 3992/5047, occupying almost the entire band, of modern tunicates. Narrow longitudinal vessels run whereas in undistorted specimens of Ausia they are 1 PALEONTOLOGICAL JOURNAL Vol. 46 No. 12012 No. 46 Vol. JOURNAL PALEONTOLOGICAL the Fig. 1. Burykhia 200 300 400 500 100 Ageneralizedstratigraphic sectionofthe 0 Lyamtsa FormationVerkhovka Formation Zimnegory Formation Yorga Formation (200 m) (130–200 m) (150–180 m) up to 200 m Padun Formation occurrences (after Fedonkin etal., 2007). occurrences(after Fedonkin (250 m) and lower and lower sublittoral sublittoral sublittoral sublittoral sublittoral sublittoral sublittoral and upper and upper Middle Coastal Coastal Coastal Middle Middle Upper Upper Upper Lower Delta shoal shoal shoal plain Highstand Tubes sabellitids resembling Tubes sabellitids resembling Beltanelloides в Vendotaenia 555.3 558.3 Lowstand algae Algae ± ± , 0.3 1 Ash level Ash level , Zolotitsa Neoproterozoic bedsofthesoutheasternWh Zimnie Lyamtsa Syuzma Gory Agma Solza Albumares brunsae Andiva ivantsovi Anfesta stankovskii Archaeaspinus fedonkini Archangelia valdaica Armillifera parva Beltanelliformis brunsae Beltanelloides sorichevae Burikhina Bomakellia kelleri Bonata septata Charnia masoni Charniodiscus sp. Cyanorus singularis Cyclomedusa cf. plana Cyclomedusa davidi Cyclomedusa delicata Cyclomedusa minuta Cyclomedusa plana Cyclomedusa radiata Dickinsonia cf. tenuis Dickinsonia costata Dickinsonia elongata ite SeaCoast;distribution offossilrem Dickinsonia lissa Ediacaria flindersi Epibalon axiferus Evmiaksia aksionovi Hiemalora stellaris Inaria limicola Inkrylovia lata Ivovicia rugulosa Karakhtia nessovi Kimberella quadrata Lossinia lissetskii Mialsemia semichatovi Nemiana simplex Nenoxites curvus Neonereites biserialis Neonereites renarius Neonereites uniserialis Nimbia occlusa Onega stepanovi Onega nenoxa Ovatoscutum concentricum Palaeopascichnus delicatus Palaeopascichnus sinuosus Palaeophragmodictya spinosa Palaeoplatoda segmentata Paliella patelliformis ains; boldlinesshow Paravendia janae Parvancorina minchami Parvancorina sagitta Pinegia stellaris Platypholinia pholiata Pomoria corolliformis Photodipleurosoma rugulosum Pseudofhizostomites howchini Pteridinium nenoxa Pteridinium simplex Ramellina pennata Rangea sp. Skolithos declinatus Solza margarita Spiriggina borealis stratigraphic levels of stratigraphic levels Staurinidia crucicula Suzmites tenuis Suzmites volutatus Tamga hamulifera Temnoxa molliuscula Tribrachidium heraldicum Vaveliksia vana Vendia janae Vendia rachiata Vendichnus vendicus Vendomia menneri Veprina undosa Vimenites bacillaris Vladimissa missarzhevskii Yelovichnus gracilis Yorgia waggoneri Zolotytsia biserialis FEDONKIN et al. et FEDONKIN 2 A NEW METAZOAN FROM THE VENDIAN OF THE WHITE SEA, RUSSIA 3 much more widely spaced. The “depressions” in the Burykhia is also somewhat different from Ausia in holotype are apparently narrower, although this is a that the “depressions” in the bands are more widely result of compaction. Many other characters differen spaced and are not as elongated, as in Ausia, although tiating these two taxa probably result from taphonomy; this could be taphonomyrelated. “Longitudinal” hence they are not included in the comparison. ridges (crests) in Ausia are not as distinct as in Burykhia. The holotype of Burykhia hunti has a smooth spherical structure near the main perforated area. Burykhia hunti Fedonkin, VickersRich, Swalla, Trusler, et Hall, sp. nov. Strangely, it was preserved in the negative relief sepa Plate 1, figs. 1, 2 rating an area filled in by a very fine limestone different Etymology. After Nathan Hunt, who promoted from the coarser matrix of the host rock. This structure the Neoproterozoic studies in Russia. was probably produced by some interior organ cavities H o l o t y p e. PIN, no. 3992/5048 (pl. 1, fig. 1), filled by sediment, possibly parts of the digestive sys coll. by M.A. Fedonkin in 1995; Russia, the right bank tem, as it is located in the same place as such structures of the Syuzma River, 5 km upstream of the mouth near are found in modern tunicates. the village of Syuzma; Vendian, Verkhovka Formation In future, if additional specimens of Burykhia and (Grazhdankin, 2003) or UstPinega Formation Ausia are found in Russia and Namibia, it could lead (Stankovsky, Sinitsyn, and Shinkarev, 1972; Stank to these two genera being synonymized. However, at ovsky, Verichev, and Dobeiko, 1985), composed of present we consider description of a new taxon as the sandstone alternating with siltstone and shale (the best option. absolute age is somewhat older than 555 ± 0.3 Ma, Material. Apart from the holotype, PIN, received for the ash beds in the Zimnie Gory Section no. 3992/5047(pl. 1, fig. 2), coll. by P. VickersRich of the White Sea Winter Coast (Martin et al., 2000). in 2003. D e s c r i p t i o n. As for the genus. The width of the ridges varies from 0.5 to 1 mm in both specimens. GEOLOGY AND TAPHONOMY The holotype also shows an area composed of longitu dinal depressions, adjacent to the imprint. G e o l o g y. The host rock is represented by fine grained and very finegrained sandstone composed Dimensions in mm. Specimen PIN mainly of angular and weakly rounded, well sorted no. 3992/5047: maximum “height,” 135; maximum quartz grains, with a small amount of feldspar grains “width,” 95 mm; mean width of perforated bands and rare flakes of biotite, oriented in parallel. The rock (bounded by continuous longitudinal ridges (crests), 5; is unstratified (massive), containing very smallsized “length” and “width” of the least distorted “depres zircon grains and rare clayey inclusions (up to about sion,” 10 and 5, respectively. Holotype PIN, 2 cm in diameter). The thin sections show abundant no. 3992/5048:
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