Qujing Ancient Fish Kingdom reappears the largest roaming Hanyu 420 million years ago

Qujing Ancient Fish Kingdom reappears the largest roaming Hanyu 420 million years ago

Qujing Ancient Fish Kingdom reproduces the largest roaming Hanyu 420 million years ago Qujing Ancient Fish Kingdom reproduces the largest roaming Hanyu 420 million years ago

Ecological restoration map of roaming Hanyu (painted by Yang Dinghua)

 Ecological restoration map of roaming Hanyu (painted by Yang Dinghua)

Comparison of gill holes between armored fish and early vertebrates (Photo courtesy of Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences)

Comparison of gill holes between armored fish and early vertebrates (Photo courtesy of Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences)

Recently, Meng Xinyuan, a master student at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, under the guidance of associate researcher Gai Zhikun, published a cover article in the Journal of Vertebrate Paleontology on the roaming of jawless armor fish 420 million years ago.
The latest research results of new materials
.

This is the first time that 30 years later, the largest real armored fish roaming Hanyu once again appeared in the "Kingdom of Ancient Fish" in Qujing, Yunnan, and revealed that it has ventral gill holes like a living devil fish, in order to explore the life habits of armored fish Provides important information
.

The largest known true armor fish

The largest known true armor fish

Roaming Hanyu ( Nochelaspis maeandrine ) was officially named by the researcher Zhu Min of the institute in 1992.
The genus Hanyu indicates that its head is big, stupid, and naive.
The species name Roaming is taken from roaming in the water for food.
Meaning
.

In the systematic classification, the roaming fish belong to the order True armored fish under the subclass Armoured fish

Nochelaspis maeandrine

Armored fishes are a group of extinct armored fishes with "helmet and armor".
They are one of the important groups to understand the transition from jawless to jawed vertebrates.
They are currently only found in China and the Silurian-mud in northern Vietnam.
The basin of the stratum has a strong aboriginal color
.

As one of the three main groups of the subclass Armorfish, the order Eurasian fish has a high species diversity, and 16 genera and species have been named

The order of the true armored fishes diverged from the backbone armored fishes as early as 450 million years ago in the Silurian Randovlevistle
.

However, compared with the large skeleton armored fishes of the same period, the early true armored fishes were very small.

The increasing evolutionary trend of the head armor of true armor fish may be related to the co-evolution of invertebrate sea scorpions during the same period
.

With the emergence of predatory function organs in the Silurian sea scorpions, their predation activities have continued to increase, and the predated real armored fishes are very capable of launching a vigorous arms race with the sea scorpions.

Thirty years later, Qujing "Ancient Fish Kingdom" reappeared

Thirty years later, Qujing "Ancient Fish Kingdom" reappeared

Wandering Hanyu was first discovered by Zhu Min in the light yellow argillaceous siltstone in the lower part of the Xishan Formation (about 420 million years ago) near the southern city gate of Qujing when Zhu Min was collecting dissertation materials in eastern Yunnan in 1987
.

The orthotype specimen is a relatively complete head armor, revealing the key morphological characteristics of the back of the head armor of the roaming fish, but unfortunately there is only one specimen, and the morphological characteristics of the ventral surface of the head armor are not preserved

The article’s corresponding author Gai Zhikun said: “For 30 years, I have been trying to find new roaming Hanyu fossils, but the fossils were found near the Nancheng Gate of the ancient city of Qujing
.

With the development of urbanization, this area It has long become a famous cultural attraction in the center of the city, and it is impossible to carry out field excavation

Another key fossil of the roaming Hanyu described this time was collected by the research team from the dark gray siltstone of the Xishancun Formation near the Miandian Reservoir in Qujing.
This is completely a new location and a new horizon.
Thanks to the construction of the Chemabi Reservoir Diversion Tunnel Project, one of the 172 major national water conservancy projects, in Qujing, a plateau water tunnel that traverses mountains and ridges leads the water from the Chemabi Reservoir to Qujing, and the tunnel outlet is opened in Qujing.
The small slope below the dam of the Qumiandian Reservoir, so a large amount of the dark gray siltstone of the Xishan Formation excavated by the tunnel excavation is stacked here.
After the continuous efforts of the research team, the third nearly complete roaming was finally found.
Hanyu's head armor
.

The first author of the article, Meng Xinyuan, said: “The new material described for roaming Hanyu fish comes from two different fossil sites in Qujing, and the upper and lower layers are slightly different, but they all have the typical characteristics of true armored fish, namely triangles.
The head armor, the longitudinal middle dorsal hole, the dorsal orbital hole, and three pairs of lateral lateral tubes
.

It is most similar in shape to the giant Yunnanogaleaspis major , a true armor fish also from the Xishancun Formation.

Yunnanogaleaspis major

In addition, the middle dorsal hole of the roaming Hanyu is a longitudinally slit shape (the ratio of length to width is greater than 6), and the head armor has a serrated edge; while the middle dorsal hole of the huge Yunnan armor fish is relatively wide and elongated.
Oval shape, the edge of the head is relatively smooth
.

Has outer gill holes like devilfish

Has outer gill holes like devilfish

It is particularly worth mentioning that the new material discovered this time reveals for the first time the secret of roaming the ventral surface of the head carapace of the fish.
Its head carapace is curved toward the ventral surface to form an abdominal ring, and the center of the abdominal ring surrounds a pear-shaped oropillary window.
The gill window is covered by a large exoskeleton plastron.
Between the plastron and the abdomen ring, 6 pairs of gill holes arranged linearly and consecutively are clearly preserved.
The gill holes are large and round, which are the gills of roaming fish.
The important opening of the capsule leading to the outside world
.

The mouth of the roaming fish may be located at the end of the gill window of the pear-shaped mouth.

Most of us humans and four-legged animals living on land breathe through our nose, mouth and lungs.
Fish lives in water.
Its main respiratory organs are not the nostrils and mouth, but the two heads.
On the side gills, there are also a few fish that occasionally use accessory respiratory organs to assist breathing
.
As the main gas exchange organ of fish, gills play an important role in the process of feeding and breathing
.
The gills of jawless and jawed species are very different
.

Under normal circumstances, the gill sacs of the jawless species are directly opened to the outside through the circular gill holes, but there are some exceptions in the case of bone beetles.
The flap covering is similar to the extant plagiobranchs.
From this point of view, the bone armor fishes are closer to the jaws than the armor fishes, and the gill holes of the armor fishes are more primitive
.

In addition, the gill sacs of roaming sacs are opened to the outside world through independent gill holes.
This is different from hagfish and heteromorphic fishes.
Their gill sacs open to the outside through a common gill hole
.

This feature of hagfish and heteromorphic fish has long been considered to be the same, that is, hagfish are regarded as heteromorphic fishes with secondary degeneration of exoskeleton.
However, fossil evidence shows that Ordovician star turtles have each other Independent outer gill holes, and hagfish in hagfish also open holes to the outside through independent gill holes
.
Therefore, the independent gill holes are more likely to represent the primitive state of vertebrates, while the total gill holes of hagfish and heteromorphs may be the result of convergent evolution
.

The outer gill holes of living lampreys, hagfish and most jawed fishes are distributed on both sides of the body.
The extinct star beetles, larval fishes, squamous fishes, and different turtles are distributed on both sides of the body.
The same is true for classes and so on
.
The armored fish represented by the roaming fish are the same as the bony armored fish, and their gill holes are located on the ventral surface of the head armor
.
The gill holes in the abdomen of the armored fish are very similar to the living devil fish
.
The devil fish, also known as the manta ray ( Mobula ), belongs to the general order of the cartilaginous fish subclass Ray
.

Mobula

The research was funded by the Frontier Science Key Research Program of the Chinese Academy of Sciences, the National Natural Science Foundation of China, and the Strategic Leading Science and Technology Special Project (Category B) of the Chinese Academy of Sciences
.
(Source: China Science News, Cui Xueqin)

Related paper information: https://doi.
org/10.
19615/j.
cnki.
2096-9899.
210727

https://doi.
org/10.
19615/j.
cnki.
2096-9899.
210727