Did humans evolve from fish from ancient times? Recently, a batch of fossils from the early stages of Silurian unveiled the mystery of our ancient fish-shaped ancestors.
What does Shiruki jawed fish look like? When did the earliest teeth appear? 440 million years ago, how many thorns are there on the newly-simplified Fanjing Mountain Fish? Why study jawless fish when exploring the origin of appendage ?
To answer this series of questions, the team of Academician Zhu Min in the Institute of Vertebrates and Paleoanthropology of the Chinese Academy of Sciences history Zhu Min published four papers in the journal Nature , namely: "The oldest complete jawed vertebrates from the early Silurian of China", "The oldest gnathostome teeth", "Spiny" (Spiny) chondrichthyan from the lower Silurian of South China, Galeaspid anatomy and the origin of vertebrate paired appendages.
picture丨The oldest and complete jawed vertebrates in the early Silurian period in China (Source: Nature)
picture丨The oldest jaw and teeth (Source: Nature)
picture丨South China China The early Silurian thorn cartilage fish in the region (Source: Nature)
Figure 丨The origin of armor fish anatomy and paired appendages of vertebrates (Source: Nature)
Academician Zhu Min's team discovered about 440 million years ago in the "Chongqing Special Buried Fossil Library" and "Guizhou Shiqian Fossil Library".
In the process of studying these fossils, the research team discovered specific characteristics of organs and structures of jaw-like organisms in the early Silurian period, which is of milestone significance for revealing the origin and evolution of ancient organisms.
Of course, this series of research results revolve around jawed vertebrates. So, what are jawed vertebrates?
jawed vertebrates are also called jawed species (Gnathostomata), and their names are derived from the two words "jaw" and "mouth" in Greek .
According to statistics, there are about 60,000 species of jaws in life, with important organ structures such as jaws, teeth, paired nostrils, necks, paired appendages. Almost all the animals we see in zoos and aquariums have jaws.
Miracle Xiushan Fish and Shen's sprig fish fossils revealed Human origin
Academician Zhu Min's team discovered the early Silurian jawed fish that was preserved from beginning to end from the Chongqing special buried fossil library.
team used CT scanning, three-dimensional reconstruction, scanning electron microscopy and other means to display the subtle anatomical structure in fossils. The results show that the human neck may have originated from this fish 436 million years ago.
Figure 丨Xiushan fish fossils and restoration (Source: Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences)
There is a horizontal fissure in the middle of the skull specimen of Xiushan fish to ensure that the head can be raised and fall during breathing and eating. This cleft forms a new boundary between the head and the trunk, which eventually evolves into the human neck. According to research, the bone fragments in front of the fissure on the top of the Xiushan Fish's head eventually evolved into the occipital bone of the human body, which is the bone directly connected to the cervical spine.
Also found in Chongqing's special buried fossil library, Shen's sprig fish with large bone armor on its shoulders. It is the ancestor of sharks, but it has ancient "armor" only found in the shield-skinned fish. It is important evidence to study how the cartilage fish where sharks are located originated.
Miracle Xiushan fish and Shen's sprig fish are only 3cm long, indicating that the jawed fish at that time were very small and adapted to the lower oxygen content in the water and atmosphere at that time.
New breakthroughs in the earliest research on the growth methods of jawed teeth
In the "Guizhou Shiqian Fossil Library", the team discovered microbody fossils of various fish species, and made new breakthroughs in the earliest research on the growth methods of jawed teeth.
Zhu Min's team carefully analyzed the tooth spiral structure of Guizhou-toothed fish more than 400 million years ago through computed tomography and three-dimensional reconstruction and restoration technology, revealing the growth and development characteristics of the earliest teeth.
Figure 丨Three-dimensional restoration of Guizhou-toothed fish (Source: Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences)
toothed fish is a tooth growth structure unique to early jawed fish. It grows in turn on a common base plate with a snail shell and coexists many new and old teeth. Guizhou-toothed fish have this very special tooth growth pattern.
The new simplified Fanjing mountain fish is full of thorns and the agile Tujia fish like a "water wing boat"
Figure 丨 Three-dimensional restoration of Fanjing mountain fish (Source: Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences)
Zhu Min's team connected the scattered spines with similar sizes and patterns in the "Shiqian Fossil Library" to restore the new simplified Fanjing mountain fish. Fanjing Mountain, Guizhou-toothed fish and Shen's sprigfish are all cartilage fish. Cartilage fish is a big family, and sharks are one of the representatives. These Silurian cartilage fish are the ancestors of sharks.
Figure丨Photoes of Lingdong Tujia Fossils and three-dimensional restoration (Source: Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences)
In one of the papers, Academician Zhu Min's team also found the complete body of the jawless armor fish "Lingdong Tujia Fish".
Research found that there is a pair of long pleated structures on both sides of the bottom of the body of the Lingdong Tujia fish, which may be the prototype of the jawed fish fins, even tetrapods and human limbs.
Using computer fluid mechanics model analysis, the fin folds of jawless "smart Tujia fish" mainly provide lift when the fish moves forward, rather than turning or directly pushing the body like the fins of jawed fish.
Whether it is Miracle Xiushan Fish, Knot Fish , or Xinshu Fanjing Mountain Fish and Lingdong Tujia Fish, they all reveal the relationship between the body structure of ancient creatures and the origin of human beings. These "sounds" from ancient times will leave a brilliant mark in the long history of human paleontology research.
Reference materials:
https://www.nature.com/articles/s41586-022-05136-8
https://www.nature .com/articles/s41586-022-05166-2
https://www.nature.com/articles/d41586-022-03080-1
https://www.nature.com /articles/s41586-022-04897-6
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