Grypania is an early, tube-shaped fossil from the
Proterozoic eon. The organism, with a size over one centimeter and consistent form, could have been a giant
bacterium, a bacterial colony, or a
eukaryoticalga.[2] The oldest probable Grypania fossils date to about 2100 million years ago (redated from the previous 1870 million)[2][3] and the youngest extended into the
Ediacaran period.[4] This implies that the time range of this taxon extended for 1200 million years.
References
^M. R. Walter, John H. Oehler & Dorothy Z. Oehler (1976). "Megascopic algae 1,300 million years old from the Belt supergroup, Montana: a reinterpretation of Walcott's Helminthoidichnites". Journal of Paleontology. 50 (5): 872–881.
JSTOR1303584.