USask, international researchers discover that modern animal life may have origins in the delta – News

0

The Cambrian Explosion over 500 million years ago saw the rapid spread of bilateral species – symmetrical along a central line, like most animals today, including humans .

The 518-million-year-old biota from Chengjiang – in Yunnan, southwest China – is one of the oldest groups of animal fossils currently known to science and a key record of the Cambrian explosion. Fossils of over 250 species have been found there, including various worms, arthropods (ancestors of living shrimp, insects, spiders, scorpions) and even early vertebrates (ancestors of fish, amphibians, reptiles, birds and mammals).

“Chengjiang’s biota, like similar faunas described elsewhere, are preserved in fine-grained deposits,” said Buatois, who is a paleontologist, sedimentologist and professor at the USask College of Arts and Science.

“Our understanding of how these muddy sediments were deposited has changed dramatically over the past 15 years.”

The new study reveals for the first time that this environment was a shallow, nutrient-rich marine delta affected by storm flooding.

“The application of this newly acquired knowledge to the study of fossiliferous deposits of exceptional preservation will radically change our understanding of how and where these sediments accumulated,” Buatois said.

The area is now on land in the mountainous province of Yunnan, but the team studied rock core samples that show evidence of sea currents in the past environment.

“The Cambrian Explosion is now universally accepted as a truly rapid evolutionary event, but the causal factors for this event have long been debated, with assumptions about environmental, genetic or ecological triggers,” said lead author Dr. Xiaoya Ma (PhD), paleobiologist at the University of Exeter and Yunnan University.

“The discovery of a deltaic environment has shed new light on understanding possible causal factors for the flourishing of these Cambrian bilateral animal-dominant marine communities and their exceptional soft-tissue preservation. Unstable environmental stressors could also contribute to the adaptive radiation of these early animals.”

“We can see from the association of many sedimentary flows that the environment hosting Chengjiang biota was complex and certainly shallower than previously suggested in the literature for similar animal communities,” the co-author said. -lead author, Dr. Farid Saleh (PhD), sedimentologist and taphonomist at Yunnan University.

Dr Changshi Qi (PhD), the other co-lead author and geochemist at Yunnan University, added: “Our research shows that Chengjiang biota mainly lived in a shallow, well-oxygenated deltaic environment. to adjacent deep, oxygen-poor environments, leading to the exceptional preservation we see today.”

The results of this study are important because they show that most early animals tolerated stressful conditions, such as fluctuations in salinity (salt) and large amounts of sediment deposition. This contrasts with previous research suggesting that similar animals colonized deeper, more stable marine environments.

“It’s hard to believe that these animals were able to cope with such a stressful environment,” said Dr. M. Gabriela Mángano (PhD), a paleontologist and USask professor who has studied other well-known preservation sites. exceptional in Canada. , Morocco and Greenland.

Dr. Maximiliano Paz (PhD), a postdoctoral researcher at USask specializing in fine-grained systems, added: “Access to sediment cores has allowed us to see details in the rock that are typically difficult to appreciate in weathered outcrops in the Chengjiang region.”

This work is an international collaboration between USask, Yunnan University, University of Exeter, Chinese Academy of Sciences, University of Lausanne and University of Leicester.

The research was funded by the Chinese Postdoctoral Science Foundation, the Natural Science Foundation of China, the State Key Laboratory of Palaeobiology and Stratigraphy, the Natural Sciences and Engineering Research Council of Canada, and the George J. McLeod Enhancement Chair in Geology.

Link to the paper: https://dx.doi.org/10.1038/s41467-022-29246-z

Share.

Comments are closed.