An international and multidisciplinary study involving the Universidad Complutense de Madrid (UCM) concludes the discovery of mineralized fossil remains of the world’s oldest – 530 million-year-old – fungi from the phosphate deposits of Fontanarejo (Ciudad Real).
These occurrences were first described about 50 years ago, but have not been studied in detail to date. Spicules were found among the fossil remains of two types of fungi, hexactinillida and demosponges – silicon units that make up the skeleton.
“It should be noted that some of the spicules are structural, that is, combined with others, virtually retaining the same status as the original organism,” emphasizes Pablo Suárez, a researcher at UCM’s Department of Geodynamics, Stratigraphy, and Paleontology. and one of the authors of a study published in Geological Journal.
Fungi can have two types of skeleton: mineralized (such as Castilian-La Mancha mushrooms), composed of structured spicules, or non-mineralized (formed by decomposing organic molecules).
“The spots of fungi in these phosphates are the oldest parts found so far, along with other examples in China, with the difference that the latter are not structural, and therefore the spots of Fontanarejo would be the oldest in such a good state of preservation.” , clarifies Suárez.
A publication published a few months ago shows fossils dating back some 890 million years that were thought to be remnants of unmineralized fungi. The spicules of Fontanarejo would thus be direct and unambiguous remnants of the oldest mushrooms in the world.
Fungi are considered to be the first evolved animals, and therefore this discovery provides new insight into the evolution of living beings.
The mollusk helps fine-tune the age of the instance
In addition to UCM, the University of Gottingen, the University of Tubingen (both in Germany) and the Nanjing Institute of Geology (China) also participated in the study.
To carry out the study, the researchers carried out fieldwork in Fontanarejo in 2019, where they conducted a geological survey and took more than 200 samples. Of these, 120 thin plates (small pieces of rock about 30 microns thick) were cut and examined by various techniques, both microscopic and chemical analysis.
Another of the main conclusions of the work is the timing of the performances. It was already known that, compared to other counterparts in the surrounding area, Fontanarejo’s occurrences belonged to the early Cambrian period (about 500-540 million years ago).
“The discovery of the remains of Anabarella, a type of mollusk, helped determine the age of about 530 million years at the end of the Cambrian period, known to geologists as Fortuniana,” Suárez says.
Microbial association in phosphates
Phosphates are mainly minerals used in the agri-food industry because they can be extracted from phosphate, which is a key element in many fertilizers.
The phosphates of Fontanarejo, on which the fungi have been petrified, retain a large body of evidence of microbial community-related origin, including the preservation of some of the filamentous forms of the original microbial deposits.
“Phosphate accumulations form very quickly after fungal death and are likely to coexist with microbial communities. This would explain the fact that fungal fossils are well preserved,” Suárez concludes.
The fungi of Fontanarejo lived in the sea along with these microbes and other organisms. The tides and storms carried all their remains to deeper waters, where they were buried under other layers of sediment, thus contributing to their survival. Millions of years later, the Variscan orogeny (which formed Pangaea) raised these strata, forming mountains whose erosion has ended up showing all these fossils on the surface of the central part of the Iberian Peninsula.
A new fossil discovery could add hundreds of millions of years to the evolutionary history of animals
Joachim Reitner et al, the revival of the phosphorite deposit in Fontanarejo (central Spain): a new window into the early Cambrian evolution of fungi and the microbial origin of phosphorites, Geological Journal (2021). DOI: 10.1017 / S001675682100087X
Provided by the Complutense University of Madrid
Quotation: The world’s oldest mineralized mushrooms found in Ciudad Real (November 20, 2021) retrieved November 17, 2021 at https://phys.org/news/2021-11-oldest-mineralized-sponges-world-ciudad.html
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