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Paleobiology of the Mesoproterozoic Billyakh Group, Anabar Uplift, Northern Siberia

Sergeev, V. N. and Knoll, A. H. and Grotzinger, J. P. (1995) Paleobiology of the Mesoproterozoic Billyakh Group, Anabar Uplift, Northern Siberia. Journal of Paleontology, 69 (1). pp. 1-37. ISSN 0022-3360.

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Silicified peritidal carbonates of the Mesoproterozoic Kotuikan and Yusmastakh Formations, Anabar Uplift, northeastern Siberia, contain exceptionally well-preserved microfossils. The assemblage is dominated by ellipsoidal akinetes of nostocalean cyanobacteria (Archaeoellipsoides) and problematic spheroidal unicells (Myxococcoides); both are allochthonous and presumably planktonic. The assemblage also includes distinctive mat-forming scytonematacean and entophysalidacean cyanobacteria, diverse short trichomes interpreted as cyanobacterial hormogonia or germinated akinetes, rare longer trichomes, and several types of colonial unicells. Although many taxa in the Kotuikan-Yusmastakh assemblage are long-ranging prokaryotes, the overall character of the assemblage is distinctly Mesoproterozoic, with its major features shared by broadly coeval floras from Canada, China, India, and elsewhere in Siberia. Microfossils also occur in middle to inner shelf shales of the Ust' -II'ya and lower Kotuikan Formations. Leiosphaerid acritarchs (up to several hundred microns in diameter) characterize this facies. As in other Mesoproterozoic acritarch assemblages, acanthomorphic and other complex forms that typify Neoproterozoic assemblages are absent. The combination in Billyakh assemblages of exceptional preservation and low eukaryotic diversity supports the hypothesis that nucleated organisms diversified markedly near the Mesoproterozoic-Neoproterozoic boundary. The assemblages also demonstrate the antiquity of cyanobacteria capable of cell differentiation and suggest the importance of both changing peritidal substrates and evolving eukaryotes in determining stratigraphic patterns of Proterozoic prokaryotes. The permineralized assemblage contains 33 species belonging to 17 genera. Ten new species or new combinations are proposed: Archaeoel/ipsoides costatus n. sp., A. elongatus n. comb., A. dolichos n. comb., A. minor n. nom., A. crassus n. comb., A. major n. comb., A. bactroformis n. sp., Veteronostoca/e medium n. sp., Filiconstrictosus cephalon n. sp., and Partitiofilum yakschinii n. sp.

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Knoll, A. H.0000-0003-1308-8585
Grotzinger, J. P.0000-0001-9324-1257
Additional Information:© 1995 The Paleontological Soctety. Accepted 30 August 1994. We thank M. A. Semikhatov and P. Petrov for valuable assistance in the field, A. Veis for informative discussion of Billyakh compression fossils, and S. Golubic for enlightening discussions of living cyanobacteria. This research was supported in part by NASA Grant NAGW 893 (to AHK), NSF Grant EAR 9058199 (to JPG), and Grant 93-05-9403 of the Russian Fund for Fundamental Research (to VNS).
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Russian Fund for Fundamental Research93-05-9403
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Record Number:CaltechAUTHORS:20130304-085557053
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ID Code:37266
Deposited By: Tony Diaz
Deposited On:06 Mar 2013 16:08
Last Modified:09 Mar 2020 13:18

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