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    Home > Food News > Food Articles > The fish from 400 million years ago tells you the secret of the formation of the jaw

    The fish from 400 million years ago tells you the secret of the formation of the jaw

    • Last Update: 2021-08-01
    • Source: Internet
    • Author: User
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    Creatures from ancient times can always provide "clues" for human beings to know and understand themselves


    Recently, the team of Zhu Min, a researcher at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, discovered a completely new and well-preserved Silurian jawed fish "pocket side town fish" in Xiushan County, Chongqing, providing new evidence for the early evolution of jaws and teeth.


    Evolutionary "mystery" spanning thousands of years

    Evolutionary "mystery" spanning thousands of years

    99.


    "The appearance of jaws is one of the most important leap in the history of life evolution.


    The origin of jaws can be traced back to the Ordovician 444 million years ago


    Zhu Youan pointed out that for a long time, people did not know exactly what the shape of the earliest jaws was, and it was also not clear how streamlined and flexible fishes like bony fishes and cartilaginous fishes were "armored" jawless.


    Since 2007, Zhu Min led a team to discover the Silurian Xiaoxiang vertebrate group in Qujing, Yunnan, including a large number of fully preserved jawed fish.


    "However, since the Silurian jawed fishes in this place have been found in the world intact, there is a view that the forms of these fishes are only the result of very specialized in a limited area.


    In order to find more Silurian jawed fish fossils and explore the truth of this issue, for many years, the early vertebrate research team has traveled across the Silurian strata across the country, and in-depth cooperation with geological survey departments in various regions, finally in Chongqing A major discovery was made in Xiushan County


    Find the second "home"

    Find the second "home"

    In the late Silurian period 423 million years ago, also known as Roderos, the ancient South China land drifted in the ocean near the equator.


    At that time, the Xiushan area of ​​Chongqing, at the turn of Hunan and Chongqing, was located in an inland sea larger than the Bohai Sea at the northern edge of the ancient South China land.


    At the end of 2019, team member Li Qiang, a postdoctoral fellow of the Chongqing Institute of Geology and Mineral Resources, surveyed the Silurian fish-bearing strata along the “Chuanhe Gaitian Road” near the border city of Hong’an in Xiushan, and accidentally discovered a complete pair of pairs in the Xiaoxi Formation of Roderos A half-open fossil of a jawed fish


    This is exactly the positive specimen of the pocket border fish! And this formation has never reported a complete jawed fish in the past


    "Although the preservation is very complete, it is not easy to study this fossil.


    The exoskeleton pattern of the Biancheng fish is similar to that of the unicornfish previously found in the Xiaoxiang fauna of Qujing, indicating that it is the same as the unicornfish, full jaw fish, and silurian fish


    An important pocket "hunter"

    An important pocket "hunter"

    Pangnathus is a kind of early jawed fishes unique to China.
    It is closely related to the origin of modern jawed vertebrates, namely the common ancestor of bony fishes and cartilaginous fishes, and has attracted great attention in recent years
    .

    The research team found through phylogenetic analysis that the pocket edge city fish preserved the mandible and mandibular teeth.
    Its lower jaw is very similar to the marginal jaws of the full jaw fish, but it has a well-developed intraoral lobe on its inner side, and five larger cones can be seen on it.
    Like teeth, the growth and arrangement of these teeth are similar to those of other scutellum fishes, especially the denticles of arthropods
    .

    Therefore, the jawbone of the border fish may be more primitive than the full jaw fish and unicornfish, which means that it is a new discovery outside of the traditional definition of "scutellin fish" such as modern fish jaws and teeth and arthropods.
    A transitional state of, provides important fossil evidence for the origin and evolution of modern jaws, including our human jaws and teeth
    .

    What makes the research team happy is that the fossils of the miniature Biancheng fish are quite intact, which allows them to unearth a lot of information that is generally not preserved.
    For example, complete fins are rarely found in the entire shield fish, and the Biancheng fish is preserved.
    This part of the structure
    .
    The fin of the border fish has a very developed fleshy "stalk"-like part covered by scales, while the fin part has only a narrow outer circle.
    This is very different from the transparent and fan-shaped fins of common fish in people's stereotypes.
    It further proves that the even fins of most primitive fishes have developed fleshy parts, while the fan-shaped transparent fins of modern radial-fin fishes, especially the bone-like fishes such as crucian carp and perch, are very specialized
    .

    "What's interesting is that the Biancheng fish is'small in size.
    ' The fossil is only 2 cm long.
    When alive, the entire fish may be only about 4 cm long, but the teeth are very large.
    The Biancheng fish may be a very fierce pocket-sized'hunter'.
    Other small animals in the environment, such as Miche's sea scorpion, Xiushan shield fish, tooth-shaped animals, etc.
    feed on
    .
    " Zhu Youan said that they would also invite cartoonist Yezi to make comic works
    .

    The study pointed out that, although the intact scutellum fish are only found in China, the comparative anatomical evidence provided by the new findings shows that the sporadic scutellum bone fragments found in the Silurian formations in Vietnam at the end of the last century are also found.
    It should belong to the full-mandibular shield skin fish, indicating that the Indosinian block and the South China block have a very close palaeogeographical relationship in the Silurian
    .

    Zhu Youan said that the pocket border fish was only the first jawed fish reported by the border city fauna.
    They also found some other jawed and jawless fossils in the same layer, and they were also found in other locations in the Silurian strata in Chongqing.
    Important fossils have been discovered and are currently under diligent research and excavation
    .
    (Source: Han Yangmei, China Science News)

    Related paper information: https://doi.
    org/10.
    1016/j.
    cub.
    2021.
    05.
    053

    https://doi.
    org/10.
    1016/j.
    cub.
    2021.
    05.
    053

     

    Provided by the comics research group of painter Yezi 

    Provided by the research group

    Photo courtesy of the Pocket Biancheng Fish Research Group

     Photo courtesy of the Pocket Biancheng Fish Research Group

     

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