The oldest organisms in France lived in the tropics.

A research team from the University of Rennes, led by Professor of Paleontology Didier Néraudeau, and bringing together master’s students from Rennes and doctoral students from Canadian universities in Alberta and Saskatchewan, have re-studyed Breton fossils known from the XIX century. In fact, the first discoveries were made by Paul Lebesconte, a Rennes pharmacist and geologist at the time. The rocks containing the fossils were formed during the Ediacaran and Cambrian geological periods, more than 530 million years (Ma) ago. These are fine slates, or slate schists, where fossils are preserved horizontally on their surface. This rediscovery and the new studies that derive from it allow a better understanding of the date, the environment of the time and the oldest fauna currently known in France.

Brittany was in the tropics

Imagine the world more than 530 Ma ago: days of only 22 hours, a generally warmer climate, unrecognizable continents and, above all, the absence of life on land! However, in the oceans everything is different: life has been diversifying and abounding for several million years. Present-day Britain was then… submerged and located near the present position of Australia! The study of the sediments associated with the fossils also informs us about the conditions of this aquatic environment. It makes us dive into relatively shallow seabeds, subject to the influence of tides and sometimes storms.

A seabed teeming with life: the proof in the footprints

There are no large fossils like in museum galleries, but traces discovered on blackboards that show the passage of animals. These fossil traces -called ichnofossils- reveal, depending on their arrangement and organization, a great deal of information about the behavior of an animal: did it move? I was resting? How did you eat? They can also inform us about the morphology of the author of the footprints.

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