Francevillian biota

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Example of macroscopic structure referred to the Francevillian biota

The Francevillian biota (Also referred to as Gabon macrofossils, Gabonionta or Francevillian group fossils) are a collection of 2.1-billion-year-old

Natural History Museum Vienna in 2014.[3] The status of the structures as fossils has been questioned.[4][5]

Part of a series on
The Francevillian basin
Geology and localities
Fossils
(Also see Akouemma)
Evolutionary concepts

Morphology

Members of the Francevillian biota
Francevillian biota macroscopic structure at display at the Natural History Museum, Vienna.

The structures are up to 17 centimetres (6.7 in) in size.[6][7] They form flattened disks with a characteristic morphology, including circular and elongated specimens. A spherical to ellipsoidal central body is bounded by radial structures. The structures show three-dimensionality and purportedly coordinated growth.[6]

A newer 2014 study by El Albani et al. describes multiple types of structures with different morphologies. There are convoluted tubes, and "string of pearls"-like structures that terminate in a "flower". This is similar to

Beltanelloides are most similar when compared to the "string of pearls".[1]

In 2023, more structures were studied by El Albani and colleagues, which were characterized by the authors as

eukaryotes. They appear to be flattened lenticular disks reaching up to 4.5 cm in diameter, with a chambered interior surrounded by a notched ridge about 1/6th of the diameter in width. The authors hypothesized this to play a role in their movement through the water column, as they suggested the organisms were likely planktonic. The structures were found to have an unusual concentration of zinc compared to the surrounding sediments, an element performing key function in eukaryote biochemistry.[2]

Locality

Geology of the Francevillian basin

The findings come from shales of the

aerobic respiration.[6]

Interpretations

In describing the structures, El Albani and colleagues described them as colonial organisms with possible affinities to

Nature, paleontologist Philip Donoghue
of Bristol University advocates a more conservative approach pending further evidence before calling them eukaryotes.

Another view, held by

pyrites.[8] El Albani et al. (2014) explicitly disputed Seilacher's interpretation.[1] A 2016 study of similar structures In Michigan, around 1.1 billion years old found them to be concretions, which the authors suggested cast doubt in the biogenicity of the Francevillian structures.[9] In a 2017 review paper Emmanuelle J. Javaux & Kevin Lepot stated that the biogenic nature of the macroscopic structures was "questionable".[4] Miao et al. 2019 stated that due to the "simple morphology and lack of diagnostic features, their eukaryotic affiliation still remains uncertain".[10] A 2023 review suggested that the structures were potentially artifacts of diagenesis, and that reliabliy distinguishing between biogenic and abiogenic structures in Paleoproterozoic rocks could be "extremely difficult", and therefore the Francevillian Biota and other supposed multicellular fossils of a similar age "currently fail to pass the stringent criteria for these structures to be viewed as bona fide fossils".[5] A 2023 isotopic analysis of the structures found that they were enriched in zinc, cobalt and nickel isotopes, with the zinc being preferentially enriched in light isotopes, which the authors suggested could represent eukaryotic metabolism. However they noted that the Francevillian Biota is still 400 million years older than is currently widely accepted for the earliest known eukaryotes.[11]

See also

Wikimedia Commons has media related to Gabonionta.

References

  1. ^
    PMID 24963687
    .
  2. ^
    S2CID 258360867
    .
  3. ^ Experiment Life – the Gabonionta. (Press Release). 4 March 2014. Naturhistorisches Museum Wien
  4. ^
    S2CID 37069547
    . The identity of the [Francevillian biota] macrostructures remains unknown and their biogenicity is questionable
  5. ^
    S2CID 257761993
    .
  6. ^
    S2CID 4331375.[permanent dead link
    ]
  7. ^ "Une vie complexe il y a 2 milliards d'années : l'hypothèse se confirme !". futura-sciences.com (in French). 26 June 2014. Retrieved 18 November 2017.
  8. doi:10.1038/news.2010.323
    .
  9. ISSN 0883-1351
    .
  10. S2CID 134362289
    .
  11. doi:10.1016/j.epsl.2023.118147
    .
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