TY - JOUR

T1 - A reassessment of the problematic Ediacaran genus Orbisiana Sokolov 1976

AU - Kolesnikov, Anton V.

AU - Liu, Alexander G.

AU - Danelian, Taniel

AU - Grazhdankin, Dmitriy V.

N1 - Publisher Copyright: © 2018 Elsevier B.V.

PY - 2018/10/1

Y1 - 2018/10/1

N2 - The genus Orbisiana was established in 1976 by B.S. Sokolov based on a collection of seven specimens within core material from a borehole drilled through the Ediacaran-age Gavrilov Yam Formation of the Moscow Basin, Russia. Here we reassess the original material for the type species Orbisiana simplex Sokolov 1976, which was long considered to be lost; fix the holotype of the type species; and revise the original diagnosis of the genus and species. Pyritisation of the fossils, which are preserved in finely laminated shales, allows three-dimensional morphological characterisation of this taxon using X-ray microtomography (μCT). Morphological and taphonomic analyses of the type material and additional three-dimensionally preserved specimens from the Verkhovka Formation (Vendian of the White Sea area) suggest that Orbisiana simplex consisted of submillimetric to millimetric globular chambers arranged in compact, grape-like clusters, or forming sinuous to linear aggregates. Occasionally, aggregates can bifurcate, with no appreciable change in chamber dimensions or shape. The phylogenetic affinity of Orbisiana remains uncertain, but its chambered construction, putative agglutinated structure of the chamber walls, and compact, occasionally branching chamber arrangement are shared with agglutinated tests of the Ediacaran genus Palaeopascichnus. Our reassessment and systematic study of the genus Orbisiana sheds new light on one of the least studied members of the late Ediacaran macroscopic biota.

AB - The genus Orbisiana was established in 1976 by B.S. Sokolov based on a collection of seven specimens within core material from a borehole drilled through the Ediacaran-age Gavrilov Yam Formation of the Moscow Basin, Russia. Here we reassess the original material for the type species Orbisiana simplex Sokolov 1976, which was long considered to be lost; fix the holotype of the type species; and revise the original diagnosis of the genus and species. Pyritisation of the fossils, which are preserved in finely laminated shales, allows three-dimensional morphological characterisation of this taxon using X-ray microtomography (μCT). Morphological and taphonomic analyses of the type material and additional three-dimensionally preserved specimens from the Verkhovka Formation (Vendian of the White Sea area) suggest that Orbisiana simplex consisted of submillimetric to millimetric globular chambers arranged in compact, grape-like clusters, or forming sinuous to linear aggregates. Occasionally, aggregates can bifurcate, with no appreciable change in chamber dimensions or shape. The phylogenetic affinity of Orbisiana remains uncertain, but its chambered construction, putative agglutinated structure of the chamber walls, and compact, occasionally branching chamber arrangement are shared with agglutinated tests of the Ediacaran genus Palaeopascichnus. Our reassessment and systematic study of the genus Orbisiana sheds new light on one of the least studied members of the late Ediacaran macroscopic biota.

KW - Agglutination

KW - East European Platform

KW - Ediacaran

KW - Gavrilov Yam Formation

KW - Moscow Basin

KW - Orbisiana

KW - Palaeopascichnus

KW - Verkhovka Formation

KW - White Sea area

KW - WHITE SEA

KW - PATTERNS

KW - ARKHANGELSK REGION

KW - TRACE FOSSIL RECORD

KW - FORAMINIFERA

KW - BIOTA

KW - EVOLUTION

KW - PYRITIZATION

KW - BASIN

KW - SOUTH CHINA

UR - http://www.scopus.com/inward/record.url?scp=85052283730&partnerID=8YFLogxK

U2 - 10.1016/j.precamres.2018.08.011

DO - 10.1016/j.precamres.2018.08.011

M3 - Article

AN - SCOPUS:85052283730

VL - 316

SP - 197

EP - 205

JO - Precambrian Research

JF - Precambrian Research

SN - 0301-9268

ER -