According to a new study, the ancestors of many animal species living today may have lived in the delta of what is now China.
During the Cambrian explosion more than 500 million years ago, bilateral species spread rapidly — symmetrically along a central line like most animals today (including humans).
The 518-million-year-old Chengjiang Biota – in Yunnan in southwestern China – is one of the oldest groups of animal fossils currently known to science and one of the most important records of the Cambrian explosion.
Fossils of more than 250 species have been found here, including various worms, arthropods (ancestors of live shrimp, insects, spiders, scorpions) and even the earliest vertebrates (ancestors of fish, amphibians, reptiles, birds and mammals).
The new study first finds that this environment was a shallow-sea, nutrient-rich delta hit by stormy floods.
The area is currently in the mainland of mountainous Yunnan Province, but the team has examined rock core samples that suggest sea currents in the past.
“The Cambrian explosion is now widely accepted as a true rapid evolutionary event, but the causal factors of this event have long been debated, along with hypotheses about environmental, genetic, or ecological triggers,” said Dr. Xiaoya Ma, a scientist. paleobiologist. the University of Exeter and Yunnan University.
“The discovery of the delta environment has shed new light on the possible causal factors for the flourishing and exceptional soft tissue conservation of marine communities dominated by Cambrian bilateral animals.
“Unstable environmental stressors may also contribute to the adaptive radiation of these early animals.”
Co-author Farid Saleh, a sedimentologist and taphonist at Yunnan University, said: “We can see from the context of many sediment flows that the environment home to the Chengjiang biota was complex and certainly shallower than previously suggested in the literature. Similar animal communities.”
Changshi Qi, the other co-author and geochemist at Yunnan University, added: “Our research shows that the Chengjiang biota lived mainly in a well-oxygenated shallow water delta environment.
“The stormy floods transported these creatures to the adjacent, deeply oxygen-deficient environment, resulting in the exceptional conservation experienced today.”
Co-author Luis Buatois, a paleontologist and sediment researcher at the University of Saskatchewan, said, “The Chengjiang biota, like the similar fauna described elsewhere, is preserved in fine-grained sediments.
“Over the past 15 years, our perception of how these muddy sediments have been deposited has changed dramatically.
“Applying recent knowledge to the study of exceptionally preserved fossil deposits will dramatically change our perception of how and where sediments accumulate.”
The results of the study are important because they show that most early animals tolerated stressful conditions such as salinity (salt) fluctuations and large amounts of sediment deposition.
This is in contrast to previous research that suggests that similar animals were colonized in deeper water, in a more stable marine environment.
“It’s hard to believe these animals were able to cope in such a stressful environmental environment,” said M. Gabriela Mángano, a paleontologist at the University of Saskatchewan who studied other well-known, exceptional conservation areas in Canada and Morocco. and Greenland.
Maximiliano Paz, a postdoctoral fellow at the University of Saskatchewan who specializes in fine-grained systems, added, “Access to sediment cores has allowed us to see details in the rock that are generally difficult to estimate on the weathered highlights of the Chengjiang area.”
This work is an international collaboration between the University of Yunnan, the University of Exeter, the University of Saskatchewan, the Chinese Academy of Sciences, the University of Lausanne and the University of Leicester.
The research was funded by the China Postdoctoral Science Foundation, the China Science Foundation, the State Key Laboratory of Paleobiology and Stratigraphy, the Canadian Council for Science and Technology Research, and the George J. McLeod Enhancement Chair in Geology.
An article published in the journal Nature Communicationsthe title is “The Chengjiang Biota Delta is inhabited.”
X-ray analysis reveals amazing 3D soft anatomy of animals that lived 500 million years ago
The Chengjiang biota was inhabited in a delta environment Nature Communications (2022). DOI: 10.1038 / s41467-022-29246-z
Provided by the University of Exeter
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