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Is Phellinites digiustoi the oldest homobasidiomycete?
American Journal of Botany
|June 29, 2011
Summary
The fossil Phellinites digiustoi, previously thought to be the oldest mushroom-forming fungus, is reidentified as conifer bark. This revises the minimum age for homobasidiomycetes to the mid-Cretaceous period.
Area of Science:
- Paleomycology
- Paleobotany
- Fungal Evolution
Background:
- The fossil Phellinites digiustoi from Patagonia was considered the oldest mushroom-forming fungus (homobasidiomycete).
- This fossil suggested an ancient origin for homobasidiomycetes, dating back to the Jurassic period.
- A significant gap of approximately 70 million years exists between P. digiustoi and the next oldest homobasidiomycete fossil in the mid-Cretaceous.
Purpose of the Study:
- To re-evaluate the taxonomic identity of Phellinites digiustoi.
- To refine the minimum age estimate for the origin of mushroom-forming fungi (homobasidiomycetes).
Main Methods:
- Microscopic examination of the holotype and a second collection of Phellinites digiustoi.
- Preparation of thin sections for cellular analysis.
- Comparison of fossil structures with known fungal and plant tissues, particularly conifer bark.
Main Results:
- Phellinites digiustoi exhibits cellular structure, confirming biological origin.
- No characteristic fungal structures such as hyphae or spores were identified.
- The fossil's morphology strongly resembles the rhytidome (outer bark) of conifers, likely from the Araucariaceae family.
Conclusions:
- Phellinites digiustoi is reclassified as fossilized conifer bark, not a homobasidiomycete.
- The direct fossil record for mushroom-forming fungi is revised, with the minimum age now established in the mid-Cretaceous.
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