A reassessment of the problematic Ediacaran genus Orbisiana Sokolov 1976 ...

• Main Authors: Kolesnikov, AV, Liu, AG, Danelian, T, Grazhdankin, DV
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier BV 2018
• Subjects: Orbisiana; Ediacaran; East European Platform; Gavrilov Yam Formation; Moscow Basin; Verkhovka Formation; White Sea area; Palaeopascichnus; Agglutination; Verkhovka; White Sea
• Online Access: https://dx.doi.org/10.17863/cam.32422; https://www.repository.cam.ac.uk/handle/1810/285052

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 simplexSokolov 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, ...