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Prototaxites, a huge, 400 million years old, fungus? Or an enormous lichen?

V. Miscellaneous

I. The fossil
II. A fungus? (Hueber)

III. An alga? (Schweitzer)
IV. A lichen? (Selosse)
VI. Literature and credits

- Some fossils of Prototaxites show shrinking cracks. Click on the lef hand photo. This phenomenon has not yet been clarified.
- Unfortunately the silicified Prototaxites in Europe are badly preserved. In most cases the quartz crystals have destroyed the inner structure. Sometimes even a pattern of pseudo cells can be observed, in which the dark organic remains form the separation between the quartz crystals (click on the right hand photo). At most some vague lines indicate where the skeletal hyphae have been. In Prototaxites from the Taunus quartzit sometimes skeletal hyphae are visible on the transverse section.

Shrinking cracks
Shrinkage cracks in Prototaxites

Pseudo cell structure

- Research has recently given indications that the chemical composition of Prototaxites points in the direction of a fungus (Boyce et al., 2003, 2007). This is not necessarily in contradiction with the lichen hypothesis because a lichen has also a fungus component.
- According to Boyce the trunk could reach the big size because it was simply growing further and further without being attacked by quadrupeds, who didn't appear until the Middle-Devonian.
Only storms could damage the trunks, but apparently they were solidly attached to the underground.
- In Australia a piece of Prototaxites  has been found with embedded remains of vascular plants, which are full of hyphae. This could be interpreted as a part of the mycelium of Prototaxites (Hueber, 2001).
- There are some reports of (indications of) branching. E.g. Altmeyer (1973) described structures resembling scars of side branches.
- Heidtke (2006) reports indications for branching inside the concentric structures in a transverse section of Prototaxites from a quarry near Birkenfeld in the Hunsrück (Germany).
- A specimen of Prototaxites from the River IJssel in the Netherlands shows a structure of skeleton hyphae on the surface and also concentrical arranged more or less circular spots. Similar specimens are known from the Isle of Spitsbergen. The occurrence of rows of spots has not yet been elucidated. Click on the photos for more details.

Prototaxites from the River IJssel
Prototaxites from the River IJssel with rows of spots

Prototaxites from Spitsbergen
Prototaxites from Spitsbergen with rows of spots

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