''Sphaerocodium'' is a fossil that represents the remains of

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

in the phylum Cyanobacteria, often called ''blue-green algae''. The species of ''Sphaerocodium'' recorded by the author Rothpletz could be symbiotic intergrowths of different encrusting organisms. Two genera ('' Rothpletzella'' and '' Wetheredella'') were proposed in 1948 by Alan Wood to include these forms in two species from the Silurian of Gotland. These acts have sometimes been misinterpreted as dividing ''Sphaerocodium'' into two genera and treating ''Sphaerocodium'' as a synonym of ''Rothpletzella'', whereas in fact ''Sphaerocodium'' is still considered a valid genus. ''Sphaerocodium'' is characterised by having dichotomously-branching tubular filaments made of

calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scra ...

, which formed encrusting masses on objects. These filaments branch in a fanlike pattern but remain in contact with each other; each filament is approximately 40-100μm wide and 30-50μ high. Filaments are not divided by septa. ''Sphaerocodium'' was formerly assigned to the now-obsolete family

porostromata "Porostromata" is an antiquated form taxon that refers to fossil cyanobacteria. The term porostromate is also used as a descriptor of textures and microstructure of stromatolites and oncolites which contain tubules or other cellular structures. ...

Fossil record

This genus is known in the fossil record from the

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. ...

to the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

(from about 460.9 to 221.5 million years ago). Fossils of species within this genus have been found in Europe, Russia, United States, Canada, China and Australia.

References

{{Taxonbar, from=Q22286463 Fossil taxa described in 1890 †Sphaerocodium Prehistoric bacteria Paleozoic life of Ontario Paleozoic life of Newfoundland and Labrador Paleozoic life of the Northwest Territories Paleozoic life of Nunavut Paleozoic life of Quebec