Deciphering the "black box" of ancient puzzles

 Although the earliest life was nearly 4 billion years ago, the earth was still a desolate microbial world for the long 3 billion years that followed. This situation changed fundamentally in the Cambrian period, about 500 million years ago. With the explosion of complex animal configurations and modern marine ecosystems during this period, the development of life entered a new animal-led era. stage. This rapid evolution event known as the "Cambrian Explosion of Life" has brought many surprises to people's understanding of the law of life evolution, but it also brought a series of "mysteries" - why animals "blowout" in the Cambrian " appears? Does their sudden appearance contradict Darwin's theory of evolution? Paleontologists are searching for answers in a treasure trove of fossils.

Our understanding of biological evolution is greatly influenced by how well fossils are preserved. Especially under normal circumstances, only hard bones are likely to be preserved as fossils, so we know very little about the soft tissues of ancient organisms. Fortunately, there are exceptions: the delicate sediments brought about by some special events can quickly seal the creatures, thereby preserving the soft body information of ancient creatures. Although this special fossil horizon is very rare, it can contain a lot of information, so it is called "extraordinary buried fossil library".

The Cambrian-specific buried fossil library provides a lot of information for people to understand the soft body anatomy and ecological behavior of animals in this period, and also makes it a "key" to understand the explosion of life in the Cambrian.

As the name suggests, the "unconventional" fossil origins of the Cambrian idiosyncratic burial fossil library are obviously not available everywhere, so where are these treasures distributed?

For more than 100 years, nearly 20 Cambrian special buried fossil banks have been discovered around the world. However, their spatiotemporal distribution is uneven, with most of them revolving around two "star" fossil repositories: the Burgess Shale and the Chengjiang Fauna.

 Researchers collect fossil specimens of Linyi fauna in the wild

In the Canadian Rocky Mountains, the Burgess Shale, about 500 million years old, is the first Cambrian exceptionally buried fossil repository discovered by humans. The Chengjiang Fauna in Yunnan, China, dating back about 520 million years ago, is well-known in the academic circles for its rich collection of exquisite soft-body structural fossils. It vividly reproduces the real face of the marine life world at that time, and is known as "one of the most amazing scientific discoveries of the 20th century".

So, can more Cambrian-specific buried fossil banks be found? Where will these "witnesses" of the Cambrian explosion of life appear?

If you want to find a new library of special buried fossils, you need to choose a potential area. Different from the South China Plate where the Chengjiang Fauna is located, the North China Plate in China was an independent block surrounded by seas on all sides in the Cambrian period, with its own unique evolutionary history.

Through long-term field work, paleontologists discovered a rich and beautifully preserved "Linyi fauna" in the mid-Cambrian strata in Linyi, Shandong on the North China Plate. After preliminary collection, more than 35 fossil groups have been found in this new special buried fossil library, of which the most diverse groups are non-trilobite arthropods represented by peculiar shrimp and Morrisons.

One of the Morrison worms is particularly striking: it has a unique shape with a long, spear-like thorn on its body, some even larger than its body length. Previously, researchers had found only a handful of specimens in North America. It appeared in the Linyi fauna, suggesting a close connection between the soft-bodied fauna of North China and North America during this period.

In addition, the Linyi fauna also contains many creatures preserved in the form of soft bodies. Most of them preserve fine anatomical structures such as appendages, digestive system, and setae. These rich information provide an important reference for further understanding the early radiation differentiation, migration and dispersal and community structure of animals after the Cambrian explosion of life.

If ordinary fossils preserve only a few words of the earth's chronicle, then the extraordinary buried fossil library provides us with more complete chapters. To unravel the secret of the explosion of life in the Cambrian period, it is necessary to have an unexpected lucky hammer, as well as rigorous and continuous efforts to find it. It is believed that with the efforts of scientists, the story about the special buried fossil bank of the Cambrian will continue to be written.