Prototaxites: Fungal Obelisks or World’s Oldest Carpet?

By Nathan Smith

A long time ago in a galaxy far far aw…..well actually in our galaxy, indeed on our planet, there existed tree-like organisms up to 8.8m tall (that’s approximately 4.5 doors tall or, for a more enjoyable measurement, roughly the size of two T-Rexs standing one on top of the other with the one on top wearing a party hat) and 1.36m wide. Found between 420 and 370 million years ago, its internal structure consisted of tiny intertwining tubes less than 50 micrometres in diameter.

Prototaxites_Dawson1888Prototaxites existed well before the developments of trees; its surrounding environment consisted of mats of moss and liverworts, populated by giant invertebrates, such as an ancient form of scorpion that could reach up to a metre long. The historical views of these structures are that they are the fossilised remains of huge external fungal structures; organic statues standing defiant in an otherwise flat landscape.  There are also suggestions that these giant structures may have had algal symbionts, and therefore should be classified as a lichen. Amongst other things, this suggestion would give good reason for why such structures became ‘extinct’ —this being that they were outcompeted by the emergence of vascular land plants in terms of being able to access the light they required.

But maybe Prototaxites aren’t fungi. Maybe they aren’t even a unique organism. There is an alternative theory; one that suggests that these giant structures weren’t signs of fungal domination but rather the results of an epic battle between nature and itself. Specifically, it suggests that the giant structures are the result of mats of liverworts being pulled up from the ground and rolled up by means of wind, water, or gravity, with algae and fungi possibly being caught up in the mix. Its evidence for this suggestion comes from the similarity in microstructure between fossilised Prototaxites and artificially created liverwort rolls, the paper being published in the American Journal of Botany in 2009.

Whether tree-like fungi or sections of liverwort torn out of the ground, Prototaxites remain a fossilised oddity of a time long since forgotten.

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