Did giant mushrooms rule the Devonian land?
As the first land plants colonised the land around the early Devonian period (419 to 359 million years ago), and the tallest trees were only a metre high, enigmatic fossils up to 8 metres tall and 1 wide were the globe’s largest surface organism, and possibly largest life form. These fossils, found worldwide and called Protoaxites, have puzzled palaeontologists since their first discovery in 1843.
Debate flowed during the time since their discovery, with four main contenders as to their identity: fungi, algae, liverworts, lichens or some kind of early tree. The anatomy of the organism is said to be evocative of many possibilities and indicative of none. A 2007 study had already suggested, based on carbon isotope and anatomical evidence, that they were fungi, but the debates continued. A fossil found in Saudi Arabia in 2008 seems to have settled the issue on the side of the fungi.
Many doubted that a mushroom could grow this big, though the same problem bedevilled the other possibilities. The silicified fossils look like giant tapering trunks, with concentric rings that resemble those of trees. However the cells in well preserved specimens are tube like, and resemble no known type of plant or fungal cell, unlike other Devonian fossils such as the early plants preserved in the Rhynie chert of Scotland.
The largest organism on Earth is still a fungus, infiltrating some 2,200 acres of forest in Oregon.
Loz
Image credit: University of Chicago
http://steurh.home.xs4all.nl/engprot/eprototx.html
http://phys.org/news185022458.html
http://www.livescience.com/1461-prehistoric-mystery-organism-humongous-fungus.html
http://news.nationalgeographic.com/news/2007/04/070425-fungus-fossil.html 2007 paper, paywall access: geology.gsapubs.org/content/35/5/399.abstract