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The Francevillian biota (also known as Gabon macrofossils or Gabonionta) is a group of 2.1-billion-year-old
Palaeoproterozoic The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6  Ga), is the first of the three sub-divisions (eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's ...
, macroscopic
organisms In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fungi; ...
known from
fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...
found in
Gabon Gabon (; ; snq, Ngabu), officially the Gabonese Republic (french: République gabonaise), is a country on the west coast of Central Africa. Located on the equator, it is bordered by Equatorial Guinea to the northwest, Cameroon to the north ...
in the Palaeoproterozoic
Francevillian B Formation The Francevillian B Formation, also known as the Francevillian Formation or FB2 in scientific research, is a geologic formation of black shale provinces close to the town of Franceville, Gabon. The formation was deposited between 2.14-2.08 Ga (b ...
, a
black shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especiall ...
province. The fossils are postulated to be evidence of the earliest form of
multicellular life A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism. All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni ...
. They were discovered by an international team led by the Moroccan-French geologist
Abderrazak El Albani Abderrazak El Albani is a French-Moroccan sedimentologist, Professor at University of Poitiers at the Hydrasa laboratory (IC2MP - CNRS). He is significant for having discovered the oldest known fossils of multicellular organisms in the 2.1 billio ...
, of the University of Poitiers, France. While they have yet to be assigned to a formal
taxonomic Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
position, they have been informally and collectively referred to as the "Gabonionta" by the
Natural History Museum Vienna The Natural History Museum Vienna (german: Naturhistorisches Museum Wien) is a large natural history museum located in Vienna, Austria. It is one of the most important natural history museums worldwide. The NHM Vienna is one of the largest museum ...
in 2014.


Morphology

The fossil organisms are up to in size. Their bodies were flattened disks with a characteristic
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...
, including circular and elongated individuals. A spherical to ellipsoidal central body is bounded by radial structures. The fossils show three-dimensionality and coordinated growth.
Cell-cell communication In biology, cell signaling (cell signalling in British English) or cell communication is the ability of a cell to receive, process, and transmit signals with its environment and with itself. Cell signaling is a fundamental property of all cellular ...
must be assumed as it existed before multi-cellularity arose. A newer 2014 study by El Albani et al. describes multiple types of fossils with different morphologies. There are convoluted tubes, and "string of pearls"-like structures that terminate in a "flower". This is similar to dictyostelid slime molds, amoebal organisms that form multicellular assemblies to migrate. However, dictyostelids are terrestrial, not marine organisms so the structures cannot simply be dictyostelids. Among known fossils, the
Ediacaran The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and th ...
''
Nemiana ''Beltanelliformis'' is a genus of discoid fossil from the Ediacaran period containing the two species B. brunsae and B. minutae, sometimes ascribed to the Ediacaran Biota. The chemical signature obtained from organically preserved specimens poin ...
'' and ''
Beltanelloides ''Beltanelliformis'' is a genus of discoid fossil from the Ediacaran period containing the two species B. brunsae and B. minutae, sometimes ascribed to the Ediacaran Biota. The chemical signature obtained from organically preserved specimens poin ...
'' are most similar when compared to the "string of pearls".


Locality

The findings come from shales of the
Franceville basin The Franceville Basin is a 1.6–2.1 billion year old sedimentary basis in Gabon. It contains unmetamorphosed sediments. It is notable for containing the Francevillian Biota, which is likely the oldest multicellular life known. A natural fission re ...
with a high fossil density of up to 40 individuals per square meter. Presumably, the organisms survived at the bottom in shallow sea water in colonies. The
geochemistry Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the e ...
of the fossil site indicates that they lived on the sediment under an oxygenated water column of a prograding delta, and they might have engaged in
aerobic respiration Cellular respiration is the process by which biological fuels are oxidised in the presence of an inorganic electron acceptor such as oxygen to produce large amounts of energy, to drive the bulk production of ATP. Cellular respiration may be des ...
.


Interpretations

In describing the fossils, El Albani and colleagues described them as colonial organisms with possible affinities to
eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
s, akin to microbial mats, albeit unlike any known structures in the fossil record, yet noting the complexity of the fossils and presence of
sterane Sterane (cyclopentanoperhydrophenanthrenes) compounds are a class of tetracyclic compounds derived from steroids or sterols via diagenetic and catagenetic degradation and saturation. Steranes have an androstane skeleton with a side chain at carb ...
as suggestive of possible eukaryote identity. In a concurrent news report in ''
Nature Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...
'', paleontologist Philip Donoghue of Bristol University advocates a more conservative approach pending further evidence before calling them eukaryotes. Another view, held by Yale's Adolf Seilacher, interprets the fossils as not organisms at all, but rather
pseudofossils Pseudofossils are inorganic objects, markings, or impressions that might be mistaken for fossils. Pseudofossils may be misleading, as some types of mineral deposits can mimic lifeforms by forming what appear to be highly detailed or organized str ...
of inorganic
pyrites The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue giv ...
. El Albani et al. (2014) explicitly disputes Seilacher's interpretation. Both pyritized and unpyritized impressions of the structures remain, as well as lightly pyritized forms. The structures formed in a single event, at the same time as the sediment. This is demonstrated by the uniform distribution of sulfur isotope ratios within the sample. In pyrite flowers, which crystallize slowly, the isotope ratio would vary within the structure. For structures that resemble pollen, chemical analysis also shows that the material in the walls of the "pollen" contains organic material.


Fate

The Francevillian biota disappears and is absent in the overlying black shale. El Albani attributes this to their extinction. The biota formed with the Great Oxidation Event, a temporary increase in atmospheric
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
, and became extinct from marine anoxia when the event was terminated by the drop in oxygen levels of the
Lomagundi event The Great Oxidation Event (GOE), also called the Great Oxygenation Event, the Oxygen Catastrophe, the Oxygen Revolution, the Oxygen Crisis, or the Oxygen Holocaust, was a time interval during the Paleoproterozoic era when the Earth's atmosphere ...
. The biota represents the earliest known experiment in multicellularity.


See also

*
Ediacaran biota The Ediacaran (; formerly Vendian) biota is a Taxonomy (biology), taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were composed of enigmatic tubular and frond-sh ...
* History of life *
Francevillian B Formation The Francevillian B Formation, also known as the Francevillian Formation or FB2 in scientific research, is a geologic formation of black shale provinces close to the town of Franceville, Gabon. The formation was deposited between 2.14-2.08 Ga (b ...
*
Franceville basin The Franceville Basin is a 1.6–2.1 billion year old sedimentary basis in Gabon. It contains unmetamorphosed sediments. It is notable for containing the Francevillian Biota, which is likely the oldest multicellular life known. A natural fission re ...


References

{{Reflist Prehistoric biotas Proterozoic life Precambrian fossils Paleoproterozoic Fossils of Gabon