The researchers used Bayesian analysis to study the decline of brachiopods and the rise of bivalves after the end-Permian extinction, and found that bivalves were better adapted to changing conditions. Left, Devonian brachiopod fossil from Ohio, USA. On the right, a recent bivalve from Shell Beach, Western Australia. Credit: (Wikimedia Commons; Creative Commons CC0 1.0 Universal Public Domain Dedication) Image on the left. The image on the right is by Zhong-Qiang Chen.
In one of the greatest crises in Earth’s history, characterized by profound changes in shellfish, brachiopods, often referred to as “lampshells”, were widely replaced by bivalves. seed such as oysters and clams. This occurred as a result of the catastrophic mass extinction at the end of the Permian period, effectively resetting the evolution of life approximately 250 million years ago.
Research carried out by paleontologists based in Bristol, UK and Wuhan, China has shed new light on this important switch as marine ecosystems changed from ancient to modern types.
Land and sea life is abundant and forms specific ecosystems. In the modern ocean, the ocean floor is home to animals such as bivalves, gastropods, corals, crustaceans, and fish. However, the history of these ecosystems all goes back to ancient times. Triassic When life comes back from the brink. During that crisis, only one in 20 species survived, and there is long debate about how new ecosystems were built and why some groups survived and others did not. was there.
Before the extinction, brachiopods were the dominant crustacean, but after the extinction, bivalves flourished and were better adapted to the new conditions.
“A classic example is the replacement of brachiopods by bivalves,” explained Zhen Guo from Wuhan and Bristol, who led the project. “Paleontologists used to say that bivalves were better competitors and would somehow outcompete brachiopods during this time of crisis. Before the extinction, brachiopods were the major group of crustaceans, and before the extinction There is no doubt that later on, bivalves took over.”
![Brachiopod and bivalve diversity over the past 500 million years](https://scitechdaily.com/images/Diversities-of-Brachiopods-and-Bivalves-Over-the-Past-500-Myr.jpg 739w,https://scitechdaily.com/images/Diversities-of-Brachiopods-and-Bivalves-Over-the-Past-500-Myr-298x400.jpg 298w)
Brachiopod and bivalve diversity over the past 500 million years. This indicates a switch between brachiopods and bivalves near the Permian-Triassic boundary.Credit: Zhen Guo et al.
“We wanted to investigate the interactions between brachiopods and bivalves throughout their long history, particularly before and after the Permian-Triassic transition,” said co-researcher Joe Flannery-Sutherland. Ta. “So we decided to use a computational method called Bayesian analysis to calculate origins, extinctions, and fossil preservation rates to test whether brachiopods and bivalves interact. For example: Did an increase in bivalves cause a decline in brachiopods?”
“In fact, we found that both groups shared similar trends in diversification dynamics throughout the crisis period,” said Professor Michael Benton, from the University of Bristol’s School of Earth Sciences. “This means that they were not actually competing with or preying on each other, but that they were both probably responding to similar external factors, such as sea temperature or short-term crises. But eventually bivalves became dominant and brachiopods retreated into the deep sea, where they still live but in reduced numbers.”
Professor Zhong-Qiang Chen from Wuhan commented:
“We always thought the end-Permian mass extinction signaled the end of brachiopods, but that was all there was to it. But both brachiopods and bivalves were hit hard by this crisis, and the Trimian Although both recovered during the 19th century, bivalves appear to have been better able to adapt to higher sea temperatures. Therefore, this gave them an advantage. Jurassic, they just exploded in numbers and the brachiopods didn’t do much. ”
Zhen Guo said: “During the research period, I had to check and compile a record of over 330,000 brachiopod and bivalve fossils, and spend weeks running Bayesian analyzes on supercomputers in Bristol. We like it because it repeats everything millions of times to account for all kinds of uncertainties in the data, giving us rich information about what’s going on.”
“The end-Permian mass extinction was the largest in history and caused a major evolutionary reset,” Professor Benton concluded. “In fact, 50 million years after the crisis, the Triassic period revolutionized life on land and sea. How life was able to return from the brink of extinction and lay the foundations for modern ecosystems. Understanding this is one of the big problems in macroevolution. But we haven’t said the last word here yet!”
Reference: “Bayesian analysis shows bivalves did not cause the extinction of brachiopods after the Permian-Triassic mass extinction” Zhen Guo, Joseph T. Flannery-Sutherland, Michael J. Benton, Zhong-Qiang Chen, September 9, 2023 nature communications.
DOI: 10.1038/s41467-023-41358-8