Fungus-like mycelial fossils in 2.4-billion-year-old vesicular basalt


Fungi have recently been found to comprise a significant part of the deep biosphere in oceanic sediments and crustal rocks. Fossils occupying fractures and pores in Phanerozoic volcanics indicate that this habitat is at least 400 million years old, but its origin may be considerably older. A 2.4-billion-year-old basalt from the Palaeoproterozoic Ongeluk Formation in South Africa contains filamentous fossils in vesicles and fractures. The filaments form mycelium-like structures growing from a basal film attached to the internal rock surfaces. Filaments branch and anastomose, touch and entangle each other. They are indistinguishable from mycelial fossils found in similar deep-biosphere habitats in the Phanerozoic, where they are attributed to fungi on the basis of chemical and morphological similarities to living fungi. The Ongeluk fossils, however, are two to three times older than current age estimates of the fungal clade. Unless they represent an unknown branch of fungus-like organisms, the fossils imply that the fungal clade is considerably older than previously thought, and that fungal origin and early evolution may lie in the oceanic deep biosphere rather than on land. The Ongeluk discovery suggests that life has inhabited submarine volcanics for more than 2.4 billion years.

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Figure 1: Geological map and stratigraphic section of the Griqualand West sub-basin, showing the location of Agouron drill hole GTF01 (28° 49′ 39.7′′ S, 23° 07′ 24.1′′ E).
Figure 2: Ongeluk vesicular basalt with filamentous fossils, petrographic thin sections.
Figure 3: Ongeluk vesicle with filamentous fossils, SRXTM surface/volume renderings; Swedish Museum of Natural History X6137.
Figure 4: Calcite- and chlorite-filled fracture with filamentous fossils in Ongeluk vesicular basalt, petrographic thin section; Swedish Museum of Natural History X6133


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Our work has been supported by the Agouron Institute, Swedish Research Council (2012-4364, 2013-4290), Danish National Research Foundation (DNRF53), Australian Research Council (DP110103660, DP140100512), Paul Scherrer Institute (20130185, 20141047), Australian Microscopy & Microanalysis Research Facility, National Science Foundation (EAR-05-45484), NASA Astrobiology Institute (NNA04CC09A), Natural Sciences and Engineering Research Council, and the European Commission CALIPSO programme (312284). We thank V. Belivanova for technical assistance, P. von Knorring for drafting Supplementary Fig. 6, J. Peckmann for supplying images for Supplementary Fig. 8c,d and A. Tehler for discussions.

Author information




A.B. provided the material and geological information; B.R. discovered the filamentous structures; S.B., B.R. and M.I. designed the study; S.B., B.R., M.I., J.M. and C.B. performed the investigation; S.B. and B.R. wrote the paper with input from other co-authors; and M.S. and F.M. designed and operated the TOMCAT beamline.

Corresponding authors

Correspondence to Stefan Bengtson or Birger Rasmussen.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Discussion; Supplementary Figures; Supplementary Tables (PDF 32681 kb)

Supplementary Video 1

Ongeluk vesicle with filamentous fossils. SRXTM surface/volume rendering, 32.5 µm thick virtual slice passing through specimen. Note NW-SE-trending thin veins connecting the vesicle with the surroundings. Swedish Museum of Natural History X6137, same vesicle as in Fig. 3. (MPG 25880 kb)

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Bengtson, S., Rasmussen, B., Ivarsson, M. et al. Fungus-like mycelial fossils in 2.4-billion-year-old vesicular basalt. Nat Ecol Evol 1, 0141 (2017).

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