After the release of the hottest movie "Aquaman" in 2018, it was warmly welcomed by many DC fans. Legend has it that the Queen of Atlantis and humans fell in love with each other and together gave birth to the crystallization of love- which was later called "Sea King" by the land people. In order to find the secret of his origins, The Sea King goes to the Sahara Desert to find the trident, the weapon left by his ancestors, which is the symbol of the atlantis throne, and with this trident, he has the ability to rule the sea. The trident is also a symbol and weapon of the sea god Poseidon in ancient Greek mythology, and it is said that when Poseidon swings it, it can not only easily set off monstrous waves, but also cause storms and tsunamis, sink the continent, collapse the heavens and the earth, and smash everything to pieces, and even cause a big earthquake. The first Chinese to take the trident may be from the Qujing "Ancient Fish Kingdom", a 410 million-year-old armor fish called the long-snouted salmon, which is said to have used its trident head armor to resist the ferocious jaws and large sea scorpions, and successfully completed thousands of kilometers of northward migration.
The long-snouted salmon is a small fish about 10 cm long, and its front snout is about 5 cm long, occupying half of the entire body length. The long-snouted trichos is classified as a suborder of jawless armorfish, named because of its head armor shape like the ancient weapon trident, and the front snout is extremely elongated, so it is figuratively called the "trident" swimming in the Devonian ocean.
The trichodermae family has always been a mysterious and unique presence in the jawless armorfish, its iconic trident-shaped head armor and half-moon nostrils, which are easily distinguishable from other armored fish, currently contain only 1 genus and 3 species, namely the long-snouted trichonch, the Zhaotong trichos and the Vietnamese trichos, which can be called the three brothers of the trichonch. Thus, the trichodermae family is also the only family of armor fish that currently contains only one genus. Because the long-snouted salmon does not have a toothed upper and lower jaw, it is also known as a jawless species, they can not take the initiative to prey, can only 'eat to open their mouths', rely on filter food seabed organic matter for a living, so mostly live in the river estuary, delta and other places close to the coast, organic debris is more abundant. The long-snouted trichonch is at the very bottom of the food chain, with thick cephalics and trident-like sharp horns and mid-dorsal spines, which may have been mainly used to defend against hunting by jawed and large invertebrates.
Figure 1 Photo of a fossil of a long-snouted salmon from the Xujiachong Formation in Qujing, Yunnan
Is there a phenomenon of return to the ancestors?
The phenomenon of atavism refers to the genetic phenomenon that some organisms accidentally appear in certain traits of the ancestors, such as a hairy child who is born with hair on the body, which is a kind of atavistic phenomenon of human hair tissue and organs. New material from Xu Jiachong's long-snouted salmon suggests that its sensory tube system is of the multi-gill type, but the new material has two more pairs of mid-transverse tubes and more lateral transverse tubes than previously described. A re-observation of the Vietnamese trichoderma from northern Vietnam shows that a second middle transverse tube is also present, only to have been mistaken in the initial description for a mid-transverse tube misplaced during the preservation process. Thus, the presence of two median transverse tubes can be seen as a new co-proximate trait of the trichodermidae family.
The double middle transverse tube was once thought to be a primitive ancestral feature of primitive armor fish. In addition, the salmon has some other similar features with the original armor fish of Dayong, Hanyang and Xiushui, for example, the half-moon shaped nostrils are somewhat similar to the transverse long fissured nostrils of the Hanyang fish, and there are three lateral transverse tubes emanating from the suborbital tube in the long-snouted trichos, and the posterior superior orbital canal in the Vietnamese trichos is funnel-shaped. According to the existing phylogenetic analysis of the suborder Armorfish, the Trichodermae family is always nested within the Order Ofs fish in South China and is closely related to the Family Duckfish and the South China Fish Family. Therefore, the morphological characteristics of the Trichodermae family and the Dayong fish family, Hanyang fish family, Xiushui fish family, etc., may not be inherited from the common ancestor, but a phenomenon of parallel evolution or regression.
Figure 2 Three brothers of the Three Fishes
a. Long-snouted trichoderma; Vietnamese salmon
The mystery of long-distance migration?
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 complete body preservation. At the same time, Mr. Liu Yuhai also reported that the Zhaotong Sanqi fish was found in the Zhaotong area of northern Yunnan in the same period. 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 the salmon may be limited to the northern part of the South China Plate.
It was not until 2002 that Zhao Wenjin and others discovered the long-snouted trichonch in Wenshan, southeastern Yunnan, and the 2009 Discovery of the Vietnamese Trichonith in northern Vietnam by The French paleontologist Philippe Jean-Vière, that people realized that the distribution range of the trichoderma was wider than originally thought, and it may be the most widely distributed genus of armor fish. However, in the geographical distribution of the north and south of the salmon, there is a geographical interval of thousands of kilometers. The long-snouted trichoderma do not have pairs of even fins for swimming, have weak swimming ability, and live mainly in benthic life. Therefore, how the salmon completed the long-distance migration has always been an unsolved mystery that plagues the paleontological community.
Figure 3. In 2017, The field excavation site of Xu Jiachong, leader of Xu Jiachong group in Qujing, Yunnan Province, during the Prague period, kissed the salmon
The first discovery of the long-snouted salmon in the "ancient fish kingdom" of Qujing, Yunnan Province, not only expands the distribution range of the salmon 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 salmon, providing important information for the study of the north-south migration route of the salmon, so it has unique biogeographic significance.
Figure 4. Ecological restoration map of the long-snouted salmon (right) and the Zhaotong three-squid fish (left) (Xinhua News Agency's report on the long-snouted salmon)