It is confirmed that the earliest vertebrate is Yunnan worm

In the process of life evolution, the evolution of vertebrates, the score of human beings, is one of the most magnificent chapters. The problem of the origin of vertebrates is always the most attractive scientific hotspot. But do you know who the earliest vertebrate is? Recently, Chinese scientists have found that Yunnan worms produced by the Cambrian Ji Chengjiang animal group 518 million years ago were the most primitive groups of vertebrates.

Yunnan insect specimen, 3.9 cm long (Zhao Fangchen's picture)

The Burgis shale animal group, Canada, about 505 million years ago and the Chengjiang Animal Group, Yunnan, China, which is about 518 million years ago, has a wealth of animal fossils characterized by soft body structures. Among them, the Bolgis shale animal groups found in 1909 produced head cabled animals pickup fish and base trunk vertebrates. A variety of ridge animals, including Yunnan worms. These fossils are the oldest spine animals in the world so far, providing precious materials for the mysteries of the origin and early evolution of vertebrates.

Researcher Chen Junyuan and others of the Institute of Palace of the Chinese Academy of Sciences made Yunnan worms as the earliest ridge animals in 1995 in the "Nature" magazine. The topic of the spine and bone was reviewed. After that, Chen Junyuan and others discovered a large number of new Yunnan worm specimens in the Haikou area of ​​Kunming. Based on the more fine anatomical structures on these specimens, they attributed Yunnan worms as the original head, thinking that its evolution position was between the head cablewood Wenchang fish and vertebrates. Due to the large differences in the interpretation of different scholars' explanation of the details of the software tissue preserved in Yunnan worms, the Yunnan worm has been classified as vertebrate, head cable animals, semi -cable animals, rear animal dry groups, and dry groups of animal organizations in 1991. Even the original symmetrical animals.

Yunnan worm ecological restoration map (directed by Zhao Fangchen, Yang Dinghua drawing)

In response to the mystery of Yunnan insect classification positions, the "Early Early Evolution of Life System" research team led by Researcher Zhu Maoyan, a researcher at the Nanjing Institute of Geological Palace of the Chinese Academy of Sciences and Professor Jiang Baoyu of the School of Earth Science and Engineering of Nanjing University in close cooperation team to use the three-dimensional X-ray fault scanning A variety of modern experimental technical methods such as microscope, Fourier infrared spectrum, Raman spectrum, scanning electron microscope, and transmitted electron microscopy, hoping to start with a micro anatomy structure to crack this mystery problem.

Based on Chen Junyuan and his collaborators in 2003, the Yunnan worm gill bow may have an important clue of cell cartilage. The research team analyzed the gill bow structure of 127 Yunnan worm specimens produced in Haikou. Found the structure of stacking cells and protein micro -original fiber structures preserved by micro -nano -scale. These two features prove that Yunnan worms have a unique pharyngeal bow that is unique to vertebrates and composed of cell cartilage, indicating that Yunnan worms belong to the original vertebrate.

Chart of Yunnan wormworm fossil pharyngeal structure

Studies also found that Yunnan worms have 7 pairs of swallow bows with similar to each other and have cell cartilage. The discovery of the 7 -pair of throat of the Yunnan worm in Yunnan insects supports the anatomy as early as the 19th century. Animal jaw bow and tongue bow and the gill bow behind are the series of homologous structures. In other words, although the pharyngeal bows in different positions of the existing vertebrates will develop into different skeletons such as jaw arch, tongue bow and gill bow, but the pharyngeal bow in different positions in the early stage of the vertebrate evolution is similar to each other.

Comparison of the formation of Yunnan insect evolution and various ridge animal pharynxuality comparison

Another important new discovery is that the 7 pairs of swallow bows of Yunnan worms are connected to the horizontal cartilage at the back of the abdomen, forming a basket -like throat. Earlier, the characteristic of Yunnan worm pharyngeal cranial in the foundation of vertebrates, supporting the more ancient ancestral characteristics.

The reviewer commented on this study: "This is a major contribution to science, and it will become a key paper in ancient vertebrate zoology. Cambrian Candy Spine vertebrate dispute. The information they show is a milestone. In the future many years, even higher resolution research is difficult to surpass "" analyzing the resolution of these fossil anatomical structures has reached the most advanced technology Limit, this is a milestone work. "

Spring City Evening News-Kaiping Journalist Yang Zhigao

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