|Grypania spiralis fossil|
Walter, Oehler & Oehler, 1976
Grypania's status as a eukaryote is not absolutely proven. It might have been a giant bacterium or bacterial colony. Its size (over one centimeter) and consistent form, suggest it is a eukaryotic alga. The oldest known Grypania fossils come from an iron mine near Negaunee, Michigan. The fossils were originally dated as 2100 million years ago, but later research showed the date as about 1874 million years ago. Grypania lasted into the Mesoproterozoic era.
- Han T.M. & Runnegar B. 1992. Megascopic eukaryotic algae from the 2.1-billion-year-old negaunee iron-formation, Michigan. Science 257 (5067): 232–235. 
- Knoll, Andrew H. et al 2006. Eukaryotic organisms in Proterozoic oceans. Philosophical Transactions of the Royal Society B 361 (1470): 1023–38. 
- Schneider D.A. et al 2006. Age constraints for Paleoproterozoic glaciation in the Lake Superior Region: detrital zircon and hydrothermal xenotime ages for the Chocolay Group, Marquette Range Supergroup. Canadian Journal of Earth Sciences 43, 571-591,