Oldest fossils of mysterious animal group are really seaweeds, study suggests
According to a recent study, a group of ancient marine animals is not as old as previously believed; their earliest fossils are seaweed.
Researchers from Yunnan University and Guizhou University in China, Durham University in the United Kingdom, and Yunnan University have discovered that the fossils that were previously believed to be the oldest Bryozoans are actually green algae.
This indicates that bryozoans, which had tentacles and lived in underwater colonies like skyscrapers, are millions of years younger than previously believed and only emerged during the Ordovician epoch (480 million years ago).
They are the only group of fossil animals that did not participate in the 40 million year-old Cambrian “explosion,” a rapid period of evolution.
The delayed appearance of bryozoans demonstrates that, contrary to popular belief, evolution proceeded to sculpt new body designs over a considerably longer time span than the Cambrian.
The magazine Nature has published the study’s findings.
Protomelission gateshousei, formerly thought to be the first Bryozoan, was discovered to have hitherto unobserved “soft parts” in ancient fossil material found in the hills of China.
The researchers were able to identify Protomelission as a member of the green algae family Dasycladales because to this delicate tissue.
Dr. Martin Smith, a co-author of the study from Durham University’s Department of Earth Sciences, said, “We frequently imagine the “Cambrian explosion” as a singular moment in evolutionary history during which all of the animal kingdom’s structural blueprints were laid out.
“The majority of future development consists of more subtle alterations to these basic body designs. But, if bryozoans really did emerge after the Cambrian period, it would demonstrate that evolution retained its creative edge even after this crucial time of innovation, suggesting that the course of life may not have been predetermined half a billion years ago.”
Professor Zhang Xiguang, a co-author of the study from Yunnan University, stated, “Our new material revealed what was living inside these chambers, unlike earlier fossils which simply maintained the skeletal framework of these early species.
“We found simple, leaf-like flanges rather than the tentacles one would anticipate in bryozoans, which led us to the conclusion that we were actually looking at seaweeds rather than fossilised animals. This indicates that it is not until the Ordovician, the following geological epoch, that the earliest compelling Bryozoan fossils are found.”
While the origin of animal groupings may not have been so quick, the researchers contend that modest seaweeds played a bigger role in the early oceans than was previously believed.
More information: Martin Smith, Protomelission is an early dasyclad alga and not a Cambrian bryozoan, Nature (2023). DOI: 10.1038/s41586-023-05775-5. www.nature.com/articles/s41586-023-05775-5
Journal information: Nature