A spectacular cache of fossils unearthed in the rural north-east of Scotland could serve as a “Rosetta Stone” for helping us to understand early life. The Rhynie chert, first discovered in 1912 near the village of the same name in Aberdeenshire, dates back some 407 million years to the early Devonian period. It is a so-called “Lagerstätte”, a sedimentary deposit containing exceptionally well-preserved fossils — in this case of ancient arthropods, cyanobacteria, fungi, lichen and seven different taxa of land plants.
A chert is a hard, fine-grained sedimentary rock composed of silica. The Rhynie chert, in particular, is believed to have formed when silica-rich waters from volcano springs flooded and petrified a land-based ecosystem in place and almost instantaneously.
A fresh analysis of the Rhynie chert undertaken by researchers from Edinburgh has revealed the preservation of the fossils at the molecular level has exceeded expectations.
The team were able to identify the chemical “fingerprints” of various organisms preserved within the rocks.
Much as the Rosetta Stone allowed Egyptologists to decipher hieroglyphics, the researchers hope these chemical codes will help them unlock the identities of some of the more ambiguous creatures preserved in the Rhynie chert.
In their study, paleobiologist Dr Corentin Loron of the University of Edinburgh and his colleagues used a non-destructive, high-resolution imaging technique known as Fourier transform infrared spectroscopy to analyse the fossils within the Rhynie chert in new detail.
By concentrating first on the fossils representing identifiable species, the team were able to identify molecular fingerprints that allowed them to distinguish between bacteria, fungi and other organisms.
These signatures have already been employed to learn more about some of the more mysterious members of the Rhynie ecosystem — including two specimens of tubular “nematophyte”.
These enigmatic organisms — which have been found in both Devonian and older, late Silurian sediments — have both algal and fungal characteristics, such that they have been hard to classify.
The new findings, however, indicate that they are unlikely to have been either types of fungi or lichen.
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Paper co-author and palaeobiologist Dr Sean McMahon, also of the University of Edinburgh, said: “We have shown how a quick, non-invasive method can be used to discriminate between different lifeforms.
“This opens a unique window on the diversity of early life on Earth.”
The researchers also experimented with feeding their data into a machine learning algorithm trained to classify the different organisms found within the Rhynie chert.
In the future, they said, the same approach might be used to sort data collected from other fossil-rich deposits.
Dr Loron said that the work highlights the potential insights that can be provided by interdisciplinary studies bridging palaeontology with fields like physics and chemistry.
He said: “Our work highlights the unique scientific importance of some of Scotland’s spectacular natural heritage and provides us with a tool for studying life in trickier, more ambiguous remnants.”
Paper co-author and palaeontologist Dr Nick Fraser of National Museums Scotland agreed, adding: “The continued development of analytical techniques provides new avenues to explore the past.
“Our new study provides one more way of peering ever-deeper into the fossil record.”
The full findings of the study were published in the journal Nature Communications.
