Prototaxites
Prototaxites Temporal range:
| |
---|---|
Branching apex of P. loganii, "Schunnemunk tree" | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Stem group: | Ascomycota |
Family: | †Prototaxitaceae Hueber |
Genus: | †Prototaxites Dawson 1859 |
Type species | |
Prototaxites loganii Dawson, 1859
| |
Species | |
| |
Synonyms | |
|
Prototaxites made up of interwoven tubes around 50 micrometres (0.0020 in) in diameter, making it by far the largest land-dwelling organism of its time.
The taxonomy of Prototaxites has long been the subject of debate. Currently, it is widely considered a fungus, but the debate is ongoing.
Morphology
With a diameter of up to 1 metre (3 ft 3 in), and a height reaching 8.8 metres (29 ft), Prototaxites fossils are remnants of by far the largest organism discovered from the period of its existence. Viewed from afar, the fossils take the form of tree-trunks, spreading slightly near their base in a fashion that suggests a connection to unpreserved root-like structures.
The similarity of these tubes to structures in the early plant Nematothallus has led to suggestions that the latter may represent leaves of Prototaxites. Unfortunately for this hypothesis, the two have never been found in connection, although this may be a consequence of their detachment after the organisms' death.[8]
History of research
First collected in 1843,
Despite the overwhelming evidence that the organism grew on land,
This idea was received with disbelief, denial and strong scepticism, but further evidence is emerging to support it.
Other recent research has suggested that Prototaxites represents a rolled-up bundle of liverworts,[21] but this interpretation has substantial difficulties.[22]
A similar genus, Nematasketum, also consists of banded and branching tubes in axial bundles; this seems to be a fungus.[23]
In 2021, Gregory Retallack described new species Prototaxites honeggeri from the Darriwilian (Middle Ordovician) age Douglas Lake Member of the Lenoir Limestone, at Douglas Dam, Tennessee, which makes the earliest appearance of this genus.[24] While Ordovician origin of this genus is mentioned by some study,[2] paleobotanist Dianne Edwards referred this study and commented "When diagnostic features are absent, such fragmentary organic materials can be misinterpreted, leading to implausible attributions".[25] Nelson and Boyce (2022) referred this study by Retallack, but considered appearance of genus is Late Silurian.[1]
A 2022 paper suggested that Prototaxites was a fungal
Ecological context
Prototaxites would have been the tallest living organism in its day by far. In comparison, the plant Cooksonia only reached 6 centimetres (2.4 in) and itself towered over the "moss forests". Invertebrates were the only other land-dwelling multi-cellular life. Prototaxites became extinct as vascular plants rose to prominence.[4] The organism could have used its tall columnar structure for spore dispersal. Alternatively, if Prototaxites contained photosynthetic structures, the height would have increased light capture.[4] The University of Chicago research team has it reconstructed as a branchless, columnar structure.[26] The presence of bio-molecules often associated with algae may suggest that the organism was covered by symbiotic (or parasitic) algae (making it in essence a huge lichen), or even that it was an alga itself.[4][27][28] However, the variability in the ratios of δ13C between specimens of Prototaxites suggest that it was heterotrophic.[1]
Prototaxites mycelia (strands) have been fossilised invading the tissue of vascular plants;[6] in turn, there is evidence of animals inhabiting Prototaxites: mazes of tubes have been found within some specimens, with the fungus re-growing into the voids, leading to speculation that the organisms' extinction may have been caused by such activity;[6] however, evidence of arthropod borings in Prototaxites has been found from the early and late Devonian, suggesting the organism survived the stress of boring for many millions of years.[29] Intriguingly, Prototaxites was bored long before plants developed a structurally equivalent woody stem, and it is possible that the borers transferred to plants when these evolved.[29]
References
- ^ S2CID 249145404.
- ^ PMID 36511419.
- ^ .
- ^ .
- .
- ^ .
- S2CID 31706785.
- ^ Jonker, F.P. (1979). "Prototaxites in the Lower Devonian". Palaeontographica B: 39–56.
- ^ A fossil specimen collected by Charles Darwin's friend Joseph Dalton Hooker, was mislaid for 163 years at the British Geological Survey offices in London ("Scientists find lost Darwin fossils in gloomy corner of British Geological Survey", Christian Science Monitor, 17 January 2012; identifying Hooker as "John Hooker").
- ^ Dawson, J.W. (1856). "Remarks on a specimen of fossil wood from the Devonian rocks, (Gaspé Sandstones) of Gaspé, Canada East". Proceedings of the American Association for the Advancement of Science. 10, Part II: 174–176.
- ^ Dawson, J.W. (1859). "On the fossil plants from the Devonian rocks of Canada". The Quarterly Journal of the Geological Society of London. 15: 477–488. On p. 485, Dawson gave this "plant" its taxonomic name Prototaxites Logani.
- ^ Carruthers, Wm. (October 1872). "On the History, Histological Structure, and Affinities of Nematophycus Logani, Carr. (Prototaxites Logani, Dawson), an Alga of Devonian Age". The Monthly Microscopical Journal. 8 (4): 160–172.
- ^ The "Taxinaea" (Taxaceae) are the grouping of conifers to which Dawson drew analogy
- ^ Almond Miller, Samuel (1877). The American Palaeozoic Fossils: A Catalogue of the Genera and Species, with Names of Authors, Dates, Places of Publication, Groups of Rocks in which Found, and the Etymology and Signification of the Words, and an Introduction Devoted to the Stratigraphical Geology of the Palaeozoic Rocks. author. pp. 35.
- ^ Seward, A. C. (Albert Charles) (1898), Fossil plants : a text-book for students of botany and geology, University Press ; New York : Macmillan, p. 192, retrieved 13 February 2016
- ISBN 9781108016001.
- ISBN 9781465606853.
- ^ Church, A.H. (1919). Botanical Memoirs No. 3: Thallassiophyta and the Subaerial Transmigrant. London, England: Oxford University Press. p. 49.
- ^ Debra Lindsay (2005) Prototaxites Dawson, 1859 or Nematophycus Carruthers, 1872: Geologists V. Botanists in the Formative Period of the Science of Paleobotany. Earth Sciences History: 2005, Vol. 24, No. 1, pp. 35-61.
- .
- PMID 21622387.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - PMID 21616859.
- .
- ^ Retallack, G.J. (2019). "Ordovician land plants and fungi from Douglas Dam, Tennessee". The Palaeobotanist. 68: 1–33.
- ISSN 0028-646X.
- ^ Prehistoric mystery organism verified as giant fungus Press release from University of Chicago, April 23, 2007.
- S2CID 21794174.
- S2CID 46073056.
- ^ .
External links
- Images and discussion of the classification of Prototaxites
- "Mystery fossil turns out to be giant fungus". ABC News Online. 2007-04-23. Retrieved 2007-04-23.
- Brahic, Catherine (2007-04-24). "Mystery prehistoric fossil verified as giant fungus". New Scientist. Retrieved 2014-07-27.
- Schultz, Colin (2013-07-17). "Long Before Trees Overtook the Land, Earth Was Covered by Giant Mushrooms". Smithsonian. Retrieved 2014-07-27.
- (broken link)Paul Stamets TED talk "Prototaxites" at 5'59"
updated: https://www.ted.com/talks/paul_stamets_6_ways_mushrooms_can_save_the_world