A microscopic multicellular fungus named Ourasphaira giraldae, which lived in an estuary environment roughly 900 million to 1 billion years ago and was unearthed in the Northern Territories of Canada, is shown in this photograph from the University of Liege, Belgium released May 22, 2019. It is the oldest-known fossil fungus.  Corentin Loron/University of Liege/Handout via REUTERS.  