TY - JOUR

T1 - Early Eukaryotes in the Lakhanda Biota (Mesoproterozoic, Southeastern Siberia)—Morphological and Geochemical Evidence

AU - Shuvalova, J. V.

AU - Nagovitsin, K. E.

AU - Duda, J. P.

AU - Parkhaev, P. Yu

N1 - Funding Information: The research was supported by the Russian Foundation for Basic Research (project no. 17-54-12077), the German Research Foundation (DFG) (project nos. DU 1450/4-1 and DU 1450/5-1). Publisher Copyright: © 2021, Pleiades Publishing, Ltd.

PY - 2021/9

Y1 - 2021/9

N2 - The Mesoproterozoic Lakhanda Group (~1030 Ma) preserves one of the most diverse communities of pre-Ediacaran eukaryotes. More precisely, the Lakhanda Biota includes more than twenty taxa that have been assigned to eukaryotes with different degrees of confidence. Eight of these taxa meet current criteria for the identification of eukaryotic fossils in ancient records. These include previously described fossils such as ornamented acritarchs (Valeria lophostriata, Trachyhystrichosphaera aimika), filamentous coenocytic organisms (Aimonema ramosa, Palaeovaucheria clavata), as well as fossils with smooth-walled envelopes and single outgrowth structures (Caudosphaera expansa, Germinosphaera bispinosa, and Jacutianema solubila). In addition to these, we found as yet undescribed fossils which share remarkable similarities with Ourasphaira giraldae, a possible higher fungi species known from the (?) Meso- to Neoproterozoic of Arctic Canada. Regardless of the exact systematic affinity, these fossils can confidently be assigned to eukaryotes because of the size and high morphological complexity. Intriguingly, the organic record of the Lakhanda Formation lacks biomarkers indicative of eukaryotes (that is, regular steranes). This finding would be in line with the idea that eukaryotes were present but not significant in Mesoproterozoic marine ecosystems. However, preliminary data from an ongoing study indicate an advanced thermal maturity of the organic matter, emphasizing that this conclusion might not be drawn with absolute confidence.

AB - The Mesoproterozoic Lakhanda Group (~1030 Ma) preserves one of the most diverse communities of pre-Ediacaran eukaryotes. More precisely, the Lakhanda Biota includes more than twenty taxa that have been assigned to eukaryotes with different degrees of confidence. Eight of these taxa meet current criteria for the identification of eukaryotic fossils in ancient records. These include previously described fossils such as ornamented acritarchs (Valeria lophostriata, Trachyhystrichosphaera aimika), filamentous coenocytic organisms (Aimonema ramosa, Palaeovaucheria clavata), as well as fossils with smooth-walled envelopes and single outgrowth structures (Caudosphaera expansa, Germinosphaera bispinosa, and Jacutianema solubila). In addition to these, we found as yet undescribed fossils which share remarkable similarities with Ourasphaira giraldae, a possible higher fungi species known from the (?) Meso- to Neoproterozoic of Arctic Canada. Regardless of the exact systematic affinity, these fossils can confidently be assigned to eukaryotes because of the size and high morphological complexity. Intriguingly, the organic record of the Lakhanda Formation lacks biomarkers indicative of eukaryotes (that is, regular steranes). This finding would be in line with the idea that eukaryotes were present but not significant in Mesoproterozoic marine ecosystems. However, preliminary data from an ongoing study indicate an advanced thermal maturity of the organic matter, emphasizing that this conclusion might not be drawn with absolute confidence.

KW - biomarkers

KW - eukaryotes

KW - Lakhanda biota

KW - Mesoproterozoic

KW - Biological Evolution

KW - Geologic Sediments

KW - Eukaryota

KW - Biota

KW - Ecosystem

KW - Siberia

KW - Fossils

UR - http://www.scopus.com/inward/record.url?scp=85118706339&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/7b578dc4-df23-3701-a05e-a2c878e98b6a/

U2 - 10.1134/S0012496621050100

DO - 10.1134/S0012496621050100

M3 - Article

C2 - 34731376

AN - SCOPUS:85118706339

VL - 500

SP - 127

EP - 132

JO - Doklady Biological Sciences

JF - Doklady Biological Sciences

SN - 0012-4966

IS - 1

M1 - 3

ER -