How did the vertebrate ancestors "wear Lin with armor" 400 million years ago?HD CT reveals

One of the most significant features of fish is the scales covered by the surface. The shape of the scales and phosphorus is an important evidence to classify the body structure, lifestyle, and each other. Recently, paleontologists used high -precision computer fault scanning technology to obtain the most complete turtle turtle high -definition scales and scales. As a result, the original characteristics of the jaw vertebrate scales have more in -depth understanding.

The results of the research were subject to "scales and scales in the root of jaw vertebrates". They were published on June 8, 2022 on the Nature-InDex publication "Elife", and were selected as "Elife Digest" special report.

▲ Xitun Deputy Yunnan fish ecological restoration map. (Yang Dinghua painted)

The scales of fish are bone, which is part of exoskeleton or membrane. The body surface covering scales is one of the most significant features of fish. These scales bear functions such as defense, offense, feeding, filtering, sensation, protecting the body from wear and preventing parasites.

In addition, the decoration of the scale surface and the structure of the abdomen can be received and guided water flow to reduce resistance. The scales are neatly arranged in a certain growth mode, which is the source of the idiom "row".

The scales and scale columns are important evidence of classifying fossil fish, speculating the body structure, lifestyle, and relationships with each other.

Shield -skinned fish is the most primitive jaw vertebrate, so the shape of its scales and scale columns has attracted much attention from scholars. The complete shield -leather fish scales are rare than the scales of hard bone fish and cartilage fish.

Yunnan Qujing Xiaxia Pen Tongluohekov Izun Xitun (about 410 million years ago) was the famous early fish fossil production area, which was preserved with a very rich shield -leather fish scales micro -fossil. However, due to the lack of complete scale columns, these large amounts of scattered shields and fish scales are difficult to get classified and identified, and the information provided is very limited.

The turtle is one of the earliest paleontological groups known to the scientific community. Beginning in the second half of the last century, primitive turtles such as Yunnan fish found in my country set off a new boom in research, but it was not until the 1990s that the complete Yunnan fish specimen -Xitun deputy Yunnan was found. Fish, vice Yunnan fish is still the best species in Yunnan fish.

Due to its original status and integrity, the deputy Yunnan fish became a key part of revealing the sequence of jaw vertebrate evolutionary sequences in the early days. The research team uses a high -precision computer fault scanning (MicroCT) technology to rebuild the scale list preserved by the vice -Yunnan fish positive model of Xitun to obtain the most complete turtle turtle high -definition scales and scales.

▲ Photo of Xitun Vice Yunnan Yu Fossil. (Photo of Wang Yajing) a) Back view; b) Right view; c) Left side view

The results of the vice Yunnan fish fossil scan show the complete scales of the most primitive jaw vertebrate. Its dorsal and tail fins are completely covered with heavy membrane scales.

The scan shows that the form of the auxiliary Yunnan fish scales has considerable differences and complex regional differentiation. The same individual scales show great diversity in the morphological characteristics of the contour, the surface of the membrane, the proportion of the crown, the pressure method, and the size.

In addition, after the longitudinal axis of the body, the scales show different gradient characteristics in different areas, especially the side scales gradually becomes larger than the longitudinal axis of the body, which is the opposite of most hard bone fish, and the scales are from each other by each other. Strong overwriting (general features of hard bone fish scales) gradually transformed into non -overwing (general features of cartilage fish).

Interestingly, the differentiation of the above -mentioned scales is simplified among the fossils of turtle turtles, and these phenomena can be observed only in the original group of turtles. The simplified scales are also independent in the cartilage fish branches, meat fin fish and spokefish branches in hard bone fish, respectively. Therefore, Vice Yunnan Fish has become the most important "window" to understand the most important "window" of the ancestral scales of the jaw vertebrate.

Deputy Yunnan fish complete scales also provide important information for scales micro fossil research. The research team was listed as a deputy Yunnan fish scales as a reference. At the same sample point and layer treatment of the deputy Yunnan fish, a group of Yunnan fish scales micro -fossils were identified and identified. Organic studies have shown that most Yunnan fish scales do not have developed intermediate loose layers (composed of bone with blood vessels), which may represent the original characteristics of jaw vertebrate scales.

Wang Yajing, a doctoral student of the Integration Center of Nanjing University Biological Evolution and Environmental Science and Education, is the first author of the paper. Academician Zhu Min, a researcher at the Institute of Ancient Human Research Institute of the Chinese Academy of Sciences, is a communication author of the dissertation. Special funding for sexual leading technology.

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Author: Xu Qimin

Editor in charge: Ren Quan

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*Wenhui exclusive manuscript, please indicate the source for reprinting.

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