Traces of old life that speak of early diversity in marine ecosystems

If we could dive the ocean floor nearly 540 million years ago, just after the point where the waves start breaking, we would find one Explosion of life, worm-shaped animals and other marine animals creating holes and complex structures in mud and sand where the environment had previously been largely sterile.

Thanks to the research published in the journal Science Advances by an international team of scientists led by the University of Saskatchewan (USask), this rapid increase in biodiversity – one of two great events of this kind over a period of 100 million years, 560 to 443 million years ago – is part of a clearer picture looming over the ancient oceans and the life of the earth within them.

“From the fossil marks – tracks, holes and caves left by animals – it is clear that this particular environment on the sea floor, the coast, served as a ‘melting pot’ for life,” said USask paleobiologist Luis Buatois, Main author of the article. “Over the next million years, life expanded from this area into deeper and shallower waters.”

The research is the result of more than 20 years of work by Buatois and the team that has examined hundreds of rock formations at locations on every continent.

“So far these two events – the Cambrian explosion and the Great Ordovician Biodiversification Event – were analyzed primarily by studying body fossils such as shells, shells and bones of ancient marine animals, “said Buatois.” We can now say with confidence that these events are also reflected in the fossil record – it reveals the work of those soft-bodied creatures whose fleshy tissues rot very quickly and are therefore very rarely preserved. “

Trilobite trace fossils during the Great Ordovician Biodiversity Event. (Photo: Luis Buatois)

For the first time, the team has shown evidence that animals are actively “designing” their Ecosystemby building abundant and varied caves at the bottom of the world’s oceans in those ancient times.

“Never underestimate what animals are capable of,” said USask paleobiologist Gabriela Mángano, co-author of the paper. “They can change their physical and chemical environment, shut out other animals or allow them to thrive by creating new resources. And of course, they did all of those things in these ancient seas.”

What these animals did that left fossil traces behind may have laid the foundation for a greater diversity of marine life. The researchers identified a gap of 20 million years ago during the Cambrian Explosion (the time when most major groups of animals first appeared in the fossil record) between diversification in fossil traces and fossils from animal bodies. suggesting that later animals took advantage of changes that allowed them to diversify even further.

The research also helps solve a big question in the geochemical record that indicated that much of the ancient ocean was lacking oxygen and unsuitable for life. Like the oceans of today, the Cambrian Ocean had certain areas full of life while others lacked the necessary conditions to sustain it.

“The fact that the distribution of fossil traces shows that there were places where life flourished alongside others that were devoid of animal activity during the early Cambrian period makes a strong case for the idea that areas of sufficient land exist Oxygen for the conservation of a wide variety of animals existed in deeper areas besides deoxygenated water, “Mángano said. “The situation is similar to that of modern oceans, with areas of minimal oxygen in the outer part of the continental shelf and the upper part of the continental slope, but with oxygenated areas in shallower waters.”

The research could provide new information from an evolutionary point of view about the importance of extensive rock formations of similar ages in Canada and elsewhere, and help society prepare for challenges ahead.

“Understanding the changes that took place at the beginning of our planet’s history could help us address the current challenges in modern oceans, particularly with regard to changes in oxygen,” Buatois said. (Source: NCYT amazement)