''Girvanella'' is a fossil thought to represent the calcified sheath of a filamentous cyanobacterium known from the Burgess Shale and other

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

fossil deposits. ''Girvanella'' was originally described as a

foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular Ectoplasm (cell biology), ectoplasm for catching food and ot ...

. It was later 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. ...

. In 2020, it was assigned to the order Oscillatoriales. ''Girvanella'' is characterised by having flexing, tubular filaments with a uniform diameter usually between 10 and 30 microns (rarely up to 100 microns). The walls of these tubules are relatively thick and calcareous. These tubules are typically (but not always) twisted together into nodules, and often encrust other objects including foraminifera. Fossils of ''Girvanella'' are found from the

through the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

. ''Girvanella'' fossils are found in a wide range of environmental conditions, most commonly shallow-shelf carbonate facies, but also in nonmarine limestones. Recent caliche deposits in

Barbados Barbados is an island country in the Lesser Antilles of the West Indies, in the Caribbean region of the Americas, and the most easterly of the Caribbean Islands. It occupies an area of and has a population of about 287,000 (2019 estimate). ...

may be referable to ''Girvanella''.

References

Oscillatoriales †Girvanella Prehistoric bacteria Burgess Shale fossils Paleozoic life of Ontario Paleozoic life of Newfoundland and Labrador Paleozoic life of the Northwest Territories Paleozoic life of Nunavut Paleozoic life of Quebec {{cyanobacteria-stub Cambrian genus extinctions