Recently, the paper published by Chinese scientists in the American journal Science, "South China Early Cambrian Burgess Shale Fossil Library - Qingjiang Biota", has once again aroused widespread concern about the study of the evolution of early life on Earth and the origin of animal phylums outside the circle.
Zhang Xingliang, Fu Dongjing and others from northwestern University in China's early life and environment innovation research team have published for the first time the 518 million-year-old Cambrian specific buried soft body fossil library found in the Changyang area of Yichang, Hubei Province, "Qingjiang Biota".
In its brief to the media, Science magazine said that "a new treasure revealing the secrets of the Cambrian period has been unearthed." The British magazine Nature said in the report: "The Qingjiang biota opens another window to observe the spectacular Cambrian, and various new biological taxa have never been seen before." ”
What kind of "new treasure" has been opened up to this breakthrough discovery that has triggered the praise of the international scientific community?
Paleontological "unsolved cases" cambrian explosion
The "Cambrian explosion of life" has been called a major "unsolved case" in paleontology and geology.
In the early Cambrian, 540 million years ago, there was one of the largest and most far-reaching biological innovations in the history of life on Earth. In less than 1% of the history of life on Earth, more than 90% of animal phyla were rapidly created. The Cambrian strata suddenly appeared a large number of invertebrates and the oldest vertebrates - the world's first fish Kunming fish fossil. However, in the more ancient strata, no obvious ancestral fossils have been found for a long time, a phenomenon known as the "Cambrian Explosion of Life", referred to as the Cambrian Explosion.
How to explain the sudden emergence of so many animal phyla in such a short period of time has been plaguing the academic community. As a result, the Cambrian explosion was listed as the "six major natural science problems" together with the origin of life and the origin of intelligence.
A new treasure that reveals the secrets of cambrianism
"To decipher the mysteries of the Cambrian explosion, we need to find reliable fossil evidence. The Burgess Shale Fossil Reservoir is the best window to explore the Cambrian explosion. Associate Professor Fu Dongjing, the first author of the paper, said.
The Burgess Shale Fossil Bank, first discovered in 1909 in the Burgess Shale of the Midcambrian Period in the Canadian Rockies, was named after it. For more than 100 years, more than 50 such fossil banks have been found around the world, among which the Burgess shale biota in Canada and the Chengjiang biota in Yunnan, China, discovered in 1984, are the most famous, becoming "ideal top research destinations".
"The Qingjiang biota is the top Burgess shale-type fossil reservoir. Subsequent excavation, research and conservation will likely provide a multifaceted scientific basis for exploring the major scientific problem of the Cambrian explosion. Fu Dongjing said.
According to reports, after preliminary research on 4351 of the large number of precious fossil specimens collected by the Qingjiang biota, 109 genera have been classified and identified, of which 53% are new genera that have never been recorded before. Moreover, most of the soft-bodied organisms in the Qingjiang biota are found, and 85% of the prozoan genera that have been found do not have mineralized bones, and the vast majority are "basic animals" without bones such as jellyfish and sea anemones.
What is even more surprising to scientists is that the fossil morphology of the Qingjiang biota is highly fidelity, the various groups of animals are preserved vividly, and the morphological structure of soft tissues and organs such as animal eyes, nerves, and internal organs is clearly visible.
Biometric "sparsity curve" analysis shows that the species diversity of the Qingjiang biota is expected to exceed all known Cambrian soft body fossil pools.
The three-act Cambrian explosion hypothesis is proposed
In recent years, under the leadership of Shu Degan, an academician of the Chinese Academy of Sciences, the early life and environmental innovation research team of Northwest University has conducted a long-term exploration of the Chengjiang biota and the Cambrian explosion, and achieved systematic innovation results.
Based on Darwin's conjecture that life on earth is "tree-shaped evolution", through decades of research and empirical evidence, the team proposed the "three-act Cambrian explosion hypothesis", outlining the basic outline of the "animal tree" of the cambrian life explosion in three stages, which created the basic outline of the three branches of basic animals, prototozoa and posterior mouth animals, and then constructed a complete early animal lineage tree framework map for the first time.
"With the development and deepening of future research work, the Qingjiang biota will find more direct evidence of biological evolution for where the 'early animal lineage trees' fork and where to branch and fall." Academician Shu Degan said.
Compared with the Chengjiang biota, the Qingjiang biota lives in deeper water environments far from the coast, representing a new biome in different ecological environments. This is confirmed by more than half of its new genera species. Therefore, the subsequent large-scale excavations of the Qingjiang biota will provide first-hand materials for the discovery and exploration of new body configurations and new animal phyla. Professor Zhang Xingliang, the corresponding author of the paper, said.
What makes Chinese scientists feel "lucky" is that the two most fidelity Burgess shale fossil banks in the world, Burgess and Chengjiang, have undergone serious geological transformations such as high temperature metamorphism and weathering after burial, and their samples can no longer be used for in-depth burial research. The soft body fossils found in the Qingjiang biota miraculously preserved the original organic matter in the form of a native carbonaceous film.
Therefore, not only in the field of paleontological research, the discovery of the Qingjiang biota is also of great value for evolutionary biology, phylogenetics, and frontier research directions in interdisciplinary disciplines such as burial, paleoecology, and geochemistry.
"The Qingjiang biota will provide ideal material for conducting buried and geochemical studies, and then for in-depth paleoenvironmental research." The problem of special burial mechanism of animal soft body structure that has plagued the academic community for many years may be cracked in the Qingjiang biota. Zhang Xingliang said.
It can be expected that with the advancement of interdisciplinary research, China's Qingjiang biota will bring us more: discover more problems, crack more mysteries... (Xu Zuhua)