Recently, the German century-old academic journal palaeobiodiversity and palaeoenvironments published online the latest research results on the Yunnan Qujing Early Devon Prague period Xu Jiachong group leader kissing sanqi fish, which was completed by Gai Zhikun and others of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences.
This is the first time this year that the scientific research team has found traces of long-snouted Sanqi fish in the "Ancient Fish Kingdom" of Qujing. The first discovery of the long-snouted salmon in the "Ancient Fish Kingdom" of Qujing enriched the morphological characteristics of the Family of Salmonidae, provided a key material for exploring the adaptation radiation of armored fish in the Early Devonian Period of the Prague Period, and was also of great significance for the study of the origin, diversity and migration of the Family of Salmonidae.
410 million years ago in Qujing, Yunnan Province, early Devonian Prague period long-snouted salmon fossil photo courtesy of Gai Zhikun
The long-snouted salmon belongs to the suborder Sangi fish family of jawless armorfish in taxonomy, because its head armor is shaped like an ancient weapon trident, and the front snout is extremely elongated (the length of the snout can reach 2.5% of the middle of the head carapace), so it can be called the "trident" swimming in the Devonian ocean. The Family Sanqi has always been a mysterious and unique presence among jawless armorfish, its iconic trident-shaped head armor and half-moon nostrils, which are easy to distinguish from other armored fish, currently contain only 1 genus and 3 species, namely long-snouted sanqi fish, Zhaotong sanqi fish and Vietnamese sanqi fish, which can be called the three brothers of sanqi fish. Thus, the Family Miki is also the only family of current armored fish that contains only one genus. Originally discovered in 1975 by Mr. Liu Yuhai, the first person to study armor fish, in the Devonian strata of Yanmen Dam in Longmen Mountain, Sichuan River, it is the first armored fish in the world with a complete body preservation. At the same time, Mr. Liu Yuhai also reported the Zhaotong Sanqi fish found in the Zhaotong area of northern Yunnan at the same time. Yunnan Zhaotong and Sichuan Jiangyou are geographically close to each other, both belonging to the northern part of the South China Plate, so it has long been believed that the living area of sanqi fish may be limited to the northern part of the South China Plate. It was not until 2002 that Zhao Wenjin et al. discovered the long-snouted sanqi fish in Wenshan, southeast yunnan, and in 2009, french paleontologist Philippe. Jean Vière discovered the Vietnamese salmon in northern Vietnam, and it was realized that the distribution range of the salmon was more extensive than originally thought, and it was probably the most widely distributed genus of armor fish. However, in the geographical distribution of Sanqi fish in the north and south, there are thousands of kilometers of geographical spacing, and how the Sanqi fish with weak swimming ability and camp benthic life has completed the long-distance migration has always been an unsolved mystery that plagues the paleontological community. The first discovery of the long-snouted Sanqi fish in the "ancient fish kingdom" of Qujing, Yunnan Province, not only expands the distribution range of sanqi fish in the South China plate, but also the Qujing area is exactly in the position between the Jiangyou region and the northern region of Vietnam, filling the geographical gap in the north-south distribution of the Sanqi fish, providing important information for the study of the north-south migration route of the Sanqi fish, so it has unique biogeographic significance.
Three brothers of Sanqi Fish: Long-nosed Sanqi Fish (left), Zhaotong Sanqi Fish (middle), Vietnamese Sanqi Fish (right) Guo Xiaocong-e
The discovery of the long-snouted salmon in Qujing has very important morphological and taxonomic significance. New material from Xu Jiachong's long-snouted Sanqi fish indicates that its sensory tube system belongs to the multi-gill type, but the new material has two more pairs of middle transverse tubes and more side transverse tubes than previously described. Re-observations of Vietnamese salmon from northern Vietnam show that there is also a second middle transverse tube, which was only misplaced in the initial description as a mid-transverse tube in the preservation process. Thus, the presence of two median transverse tubes can be seen as a new co-proximate trait of the family Michiidae. The double middle transverse pipe was once considered to be the original feature of the primitive armor fish Dayong fish, Hanyang fish and Xiushui fish. In addition, Sanqi fish has some other similar features with Dayong fish, Hanyang fish and Xiushui fish, for example, the half-moon shaped nostrils are somewhat similar to the transverse long fissured nostrils of The Xiushui fish Hanyang fish, and there are three lateral transverse tubes emanating from the suborbital tube in the long-snouted Sanqi fish, and the posterior superior orbital tube in the Vietnamese Sanqi fish is funnel-shaped. According to the existing phylogenetic analysis of the suborder Armorfish, the Sanqi family is always nested within the Order of Fish in South China and is relatively closely related to the Family of Ducksnocks and the Family of South China Fishes. Therefore, the morphological characteristics of the Sanqi family and the Dayong fish family, Hanyang fish family, Xiushui fish family, etc., may not be inherited from the common ancestor, which indicates that there are a large number of parallel evolutions or regression phenomena in the process of armor fish radiation evolution.
Swimming "Trident": Long-snouted Sanqi Fish (right) and Zhaotong Sanqi Fish (left) Ecological Restoration Diagram Yang Dinghua Painting
The discovery of the long-snouted sanqi fish in Qujing also has very important paleogeographic significance. The five fossil sites where the Sanqi fish are distributed belong to the South China Plate and are composed of Yangzi ancient land and Huaxia ancient land. During the Pre-Devonian Period, the South China Plate was located in the low-latitude paleoecarbon region and was isolated from the ancient continents of Lauya and Gondwana by the Guttes Andesian Oceans and the Paleo-Pacific Ocean. There is a land surface bay between the Yangtze ancient land and the Ancient Chinese land, that is, the South China Sea (Figure 4). About 420 million years ago (lokhkaov period), there was a coastal invasion in southern China, which extended from the southwest to central and western Guangxi. Beginning about 410 million years ago (Prague period), after the Guangxi Orogeny, the South China Sea covered most of the southern edge of the South China Plate, which allowed the South China Plate to develop a wide range of fossil-bearing siliceous clastic rocks and limestones in the South China Plate, such as the Nagaoling Formation of Liujing in Guangxi, the Xujiachong Formation in Qujing, the Posongchong Formation in Zhaotong, the Posongchong Formation in Wenshan, the Guanshan Slope Formation in Jiangyou, the Cangwu Formation in Wuzhou, the Khao Loc Formation and the Si Ka Formation in northern Vietnam, all of which are nearshore to delta facies deposits near the South China Sea. It provided a favorable sedimentary environment for the preservation of fossils of plants, fish and brachiopods in this period. At this time, the paleo-fish combination, the early vascular plant combination and the invertebrate brachiopod Tokyo stone swallow ('spirifer' tonkinensis) combined appearance, showing a high degree of similar endemic color, and the fauna in other parts of the world is obviously different, for example, although there are a large number of early Devonian fish fossils found in Australia, North America, Europe and Siberia, it is significantly different from the appearance of early Devonian paleo-fish in The South China Plate. In particular, the fossils of jawless armored fish and shield fish Yunnan fish in the South China Plate show a strong indigenous color. In 1981, the famous Australian paleo-fish scholar Gavin M. For the first time, Gavin c. young used paleofish from the Early Devonian South China Plate as a separate fauna and named it the "Armorfish-Yunnan Fish" fauna. Combined evidence shows that today's Yunnan-Guizhou Plateau and Guangxi region, 410 million years ago, in the Early Devonian Period, was a nearly closed land surface bay, the South China Sea, with an intermittent southward opening, forming a closed environment similar to the modern Red Sea. Due to the closed sea effect, an independent biological evolutionary region is formed, known as the biodiversity hotspot, in which organisms evolve independently, showing high diversity and strong indigenousness.
The discovery of the long-snouted sanqi fish in Qujing also has very important biological stratigraphic significance. Sanqi fish is the only armored fish among the armor fish that appeared in the Xujiachong Formation of Qujing, Yunnan, Wenshan, Zhaotong, Sichuan Jiangyouguan, Vietnam, and Nanning Nagaoling Formation, thus providing the most direct paleometry evidence for their comparison. In particular, the Vietnamese Si Ka group of Vietnamese salmon, because of its symbiosis with the Liao Jiao Shan multi-gill, the famous French paleontologist Philippe. Jean Vière has always believed that its emergence was slightly earlier than the era of The Chinese Sanqi fish, belonging to the early Devonian Lokhkaov period (about 420 million years ago). However, recent evidence of paleontological fossils suggests that the gill of LiaoJiaoShan has a longer period of continuation, possibly from the Early Devonian Lokhkaov period (about 420 million years ago) to the Early Devonian Prague period (about 410 million years ago). Sanqi fish is an important member of the Xu Jia Chong combination, through the comprehensive comparison of 8 fish-bearing strata of the Early Devonian in southern China and northern Vietnam, it is shown that the strata of these non-marine Sanqi fish can be compared with the transitional layer between the Lianhuashan Formation and the Nagaoling Formation in the Liujing Section of Guangxi (Figure 5), and the bottom of the Nagaoling contains the era of the Prague period tooth-shaped standardized stone. Therefore, the upper part of the si ka group in northern Vietnam and the upper part of the Lotus Hill group in Guangxi should be the Prague period, not the Lokhkaov period. The paleo-fish fossil assemblage of the Prague period of the South China Plate records in detail the rapid radiation evolution of armored fish, especially South China fish, in the Early Devonian.
The first author and corresponding author of the article are Gai Zhikun and Zhu Min, associate researchers of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, respectively, and the second author is Jiang Wenyu, an undergraduate student from Shandong University of Science and Technology, and researchers from Qujing Normal University. Jiang Wenyu is one of the recipients of the 2018 "Science and Technology Innovation Program" for college students in our institute, and carries out related work under the guidance of Associate Researcher Gai Zhikun. In the form of a project, the "Science and Technology Innovation Program" subsidizes outstanding students in the second or third year of science and engineering majors in various universities across the country to carry out scientific research and innovation practice activities from June to December at the Institute of Ancient Spine, which is another remarkable achievement since the implementation of the "Science and Technology Innovation Plan" for college students in my institute. The research has been funded by the National Natural Science Foundation of China, the Key Research Program of Frontier Science of the Chinese Academy of Sciences, and the Strategic Pilot Science and Technology Special Project (Category B) of the Chinese Academy of Sciences.
Source: The Paper