Prototaxites is the name of a kind Fossile, probably large Champignon S dating from the Dévonien and the Silurien (between 420 and 350 million years). Prototaxites were to form great structures being able to reach one meter of circumference at the base and up to eight meters in height. This organization would have been the greatest living organism at that time.

History

a conifer?

The fossils of Prototaxites resemble petrified pieces of wood coarsely and they can present concentric circles which point out rings of growth. This explains why Prototaxites was initially interpreted as the wood of a Conifère partly broken up by mushrooms by John William Dawson, a Canadian scientist which made the first discovered ones in 1859. Dawson described a " in particular; tronc" area of Gaspé (Canada) which was long of more than 2 m and broad 91 cm.

an alga? A mushroom? A lichen?

Since 1872, the interpretation of Dawson was criticized by Carruthers. Indeed, the anatomical study of Prototaxites reveals that it does not have cells similar to those of the terrestrial plants but of the " tubes". Carruthers re-elects Prototaxites , whose name means about " first if" /" first conifère" , Nematophycus . It compares it with mushrooms, the lichens and the algae and considers finally that being given its age, it can be a question only of one alga.

In 1919, A.H. Church suggests that being given the size which certain current mushrooms can reach, it is completely possible that Prototaxites is a mushroom. this remark was not taken into account and, although the obviousness that Prototaxites was a terrestrial organization is large, there remained classified in the algae.

In 2001, after twenty years of research, Francis Hueber, of the National Museum off Natural History of Washington starts again this assumption while being based on a detailed anatomical study and new specimens coming from Canada, of Saudi Arabia and Australia. He interprets Prototaxites like the perennial sporophore of a mushroom and proposes a rebuilding. This idea appeared rather extraordinary: among the many problems which they raised it there with the nutrition of Prototaxites . A heterotrophic mushroom of such a size would need a great quantity of organic matter to nourish itself. However at the time where he lived, there was theoretically little vegetation and thus little food available. Moreover one does not know the spores of Prototaxites .

In 2002, Marc André Selosse, professor at the university Montpellier 2, put forth the assumption that Prototaxites was a lichen: the association of an alga and a mushroom. This assumption made it possible to include/understand from which the resources came from Prototaxites (organic matter AND photosynthesis). Moreover certain lichens can have an only vegetative reproduction what would explain the absence of spores.

Lastly, in 2007, from the analyzes of the Isotope S of carbon present in these fossils, came to reinforce the assumption " champignon" and show a difference between the fossils of plants and those of Prototaxites .

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