Revision of the Problematic Vendian Macrofossil Beltanelliformis (=Beltanelloides, Nemiana) A
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ISSN 00310301, Paleontological Journal, 2014, Vol. 48, No. 13, pp. 1–26. © Pleiades Publishing, Ltd., 2014. Revision of the Problematic Vendian Macrofossil Beltanelliformis (=Beltanelloides, Nemiana) A. Yu. Ivantsova, V. P. Gritsenkob, L. I. Konstantinenko†, and M. A. Zakrevskayaa aBorissiak Paleontological Institute, Russian Academy of Sciences, Profsoyuznaya ul. 123, Moscow, 117997 Russia email: [email protected] bNational Museum of Natural History, National Academy of Sciences of Ukraine, ul. Bohdana Khmelnitskogo 15, Kiev, 01030 Ukraine cInstitute of Geological Sciences, National Academy of Sciences of Ukraine, ul. O. Gonchara 55b, Kiev, 01054 Ukraine Received December 12, 2013 Abstract—Two groups of Precambrian macrofossils are reexamined. Members of the first group are usually determined as Nemiana simplex Palij, 1976 and regarded as remains of animal organisms; members of the sec ond are often determined as Beltanelloides sorichevae Sokolov, 1965 and assigned to green algae or cyanobac teria. The cooccurrence of the two groups in burials of the White Sea outcrops, the similarity in morphology, and the presence of transitional forms suggest that they could have been variants of preservation of the same extinct species. As a result of critical analysis of published data and examination of available type specimens, the species Beltanelliformis brunsae Menner, 1974, Beltanelloides podolicus A. Istchenko, 1988, Hagenetta aaren sis Hahn et Pflug, 1988, Medusinites paliji Gureev, 1987, and Namamedusium wendti Zessin, 2008 are assigned to the same species. Beltanelliformis brunsae is regarded as the senior synonym. Taphonomic and comparative morphological data and the SEM study of phosphatized remains of Beltanelliformis agree with the hypothesis developed by M. Steiner of the microbial nature of these fossils. It is proposed that round col onies of B. brunsae grew in the area of extremely shallow water in Late Vendian marine basins. Beltanellifor mis minutae McIlroy et al., 2005 is the second species of the same genus; it was more tolerant of changes in 1 salinity and shows a wider stratigraphic range, while the species Nemiana bakeevi Becker, 1992 and Beltanel loides amorphus Menasova, 2003 are considered to have nothing in common with the groups and genus dis cussed. Keywords: Beltanelliformis, Beltanelloides, Hagenetta, Medusinites, Namamedusium, Nemiana, Vendian, southeastern White Sea, Podolia, Yakutia, Namibia DOI: 10.1134/S0031030114130036 † INTRODUCTION loides amorphus Menasova, 2003. All species, except for the last two, completely lack primary sculpturing or Late Proterozoic deposits of many regions of the internal structures, show intense postmortal compres Earth often enclose relatively large (up to several cen sion, and are capable of forming abundant monospe timeters in diameter), simply organized round struc cies accumulations, in which the outlines of crowded tures, the socalled cyclic fossils. They occur in both individuals sometimes change from initially circular to terrigenous and carbonate sections, coarse and fine polygonal. They are sometimes arranged in layers grain rocks, sometimes preserved as threedimen unseparated by sediment, but neither cut each other sional molds at the soles of sand lenses and, some times, as flat imprints inside layers of clayey or clayey– nor fuse. Nemiana bakeevi and Beltanelloides amor carbonate deposits. To date, the following ten species phus do not show evident distinctive features, so that of six genera of these fossils have been described: Bel they were probably erroneously referred to these gen tanelloides sorichevae Sokolov, 1965, Beltanelliformis era. Other species should be divided into two groups brunsae Menner, 1974, Nemiana simplex Palij, 1976, termed here “Nemiana” and “Beltanelloides” (see also Medusinites paliji Gureev, 1987, Beltanelloides podoli Narbonne and Hofmann, 1987). In a typical case, cus A. Istchenko, 1988, Hagenetta aarensis Hahn et “Nemiana” (Nemiana, Medusinites, Hagenetta, Pflug, 1988, Beltanelliformis minutae McIlroy, Crimes Namamedusium, and in part Beltanelliformis brunsae) et Pauley, 2005, Namamedusium wendti Zessin, 2008 looks like a low nodule circular in plan view, convex 1 and also Nemiana bakeevi Becker, 1992 and Beltanel from below, with a smooth surface, or flattened, with concentric folds of contortion at the lateral edges. A † Deceased. nodule is sometimes threedimensional, completely 1 2 IVANTSOV et al. separated from enclosing matter not only from below, are housed in the richest collection of Vendian fossils but also from above. In this case, its apex occasionally of the Borissiak Paleontological Institute of the Rus has a small depression. It is commonly believed that sian Academy of Sciences, Moscow (PIN). Results of this is the internal or external body mold. “Beltanel the study of this collection and type specimens of Bel loides” (Beltanelloides sorichevae, B. podolicus, and tanelloides podolicus, B. amorphus, Medusinites paliji, Beltanelliformis) is preserved in the shape of a flat or and N. simplex, which are stored in the National slightly convex imprint, smooth in the center and hav Museum of Natural History of the National Academy ing concentric folds at the periphery. Imprints of “Bel of Sciences of Ukraine, Kiev (NNPM) and Taras tanelloides” frequently have modified organic matter Shevchenko Kiev National University of Kiev of its body. In the Khatyspyt Formation of the Olenek (KNU), are considered in the present paper. Uplift, specimens with traces of slight syndiagenetic phosphatization of this substance have been found. A number of researchers believe that “Nemiana” inhab HISTORY OF THE STUDY ited hydrodynamically active shallow waters and all of In the 1920s, a school teacher from the village of their remains have been recorded in their habitats in Ozarintsy of the Mogilev District transferred several the lifetime positions. On the contrary, “Beltanel plates with round imprints coming from the beds dated loides” followed a planktonic mode of life and were then as Silurian sandstones to the Museum of the buried in relatively quiet, probably more deepwater Geological Laboratory of the Ukrainian Academy of conditions. The majority of species were marine and Sciences. The name of this teacher is not known; how only Beltanelliformis minutae could dwell in freshwater ever, he probably helped the geologist A.V. Krasovsky basins (Callow et al., 2011). Remains of B. brunsae in investigations in the vicinity of the town of Mogi sometimes cooccur within the same member with lev–Podolskii as early as 1913. In the only publication feeding traces of Proarticulata and Kimberella concerning these studies, which was named “a prelim (Epibaion sp., and Kimberichnus teruzzii Ivantsov, 2013) inary report,” Krasovsky (1916) mentioned by the way and also various remains of palaeopascichnids or even the finds of Silurian sandstone pieces with ripples and on the same bedding surfaces. A large specimen of Edi imprints resembling traces of rain drops. Kaptarenko acaria sp. overlain by molds of Nemiana simplex has (1928), who looked through the material from been found (Fedonkin et al., 2007, textfig. 282). Bel Ozarintsy and familiarized herself with the studies by tanelloides sorichevae is sometimes accompanied by Krasovsky, was sure that he considered the imprints Palaeopascichnus sp. and, sometimes, by the macro brought to Kiev. Thus, early finds were made not later phyte Archyfasma sp. (Leonov, 2007a, 2007b). Burial than 1913 and Podolia is the third known locality in conditions of these forms were common for some the world (along with Newfoundland and Namibia) of other Vendian macroorganisms. Vendian macrofossils (Fedonkin et al., 2007). The A generally accepted system of the two groups has geologists who paid attention to “sandy bubbles” from not been elaborated. The species composing them are Podolia initially regarded them as traces (Pl. 1, fig. 1). often combined in different variants. It has also been In particular, Lungershausen (1939) was sure that they proposed that all of these forms belong to only one are traces of air bubbles which were pressed out of species. Their nature is also discussed. Threedimen coastal sand by incoming waves and Stashchuk (1958) sional molds are regarded as remains benthic Meta proposed that these are pits formed by drops of water zoa: polyps (Palij 1976; Palij et al., 1979; Fedonkin, regularly falling from a hypothetical eave. Voznes 1981, 1987; Gureev, 1985, 1987; Vendskaya sistema …, ens’ky (1956) compared them to burrows produced by 1985; Zessin, 2008; Grazhdankin et al., 2010); extant larval amphibians. However, even Kaptarenko sponges (Leonov, 2007b); or animals closely related to considered the hypotheses of abiogenic origin of fos brachiopods (Hahn and Pflug, 1988); while flat sils from Podolia and rejected them. Based on a thor imprints were considered to represent planktonic or ough description of both fossil remains and geological benthic green algae (Sokolov, 1976, 1997; Xiao et al., conditions in which they occur, she proposed that they 2002; Xiao and Dong, 2006; Leonov, 2007a) or colo are of animal origin and convincingly compared them nial bacteria (Steiner, 1997; Steiner and Reitner, with imprints of jellyfish bodies (Kaptarenko, 1928). 2001). The validity of these interpretations, particu ZaikaNovatsky and Palij (1968, 1974) initially pro larly in the case of assignment of forms from different posed that these are imprints of jellyfishes and desig groups to one species, is doubtful.