Information on ichthyosaurs.

In the first half of 2000, the Yichang Institute of Geology team’s geological work in Guanling, Guizhou lasted for more than two months. It was a breathtaking experience for all members of the team.

Buried in the Guanling strata is a huge kingdom of paleontology. They are intact and have different postures. After sleeping for hundreds of millions of years, they still show the overall survival status of a biological community. This is a rare group of biological fossils in the world. For geologists, they are facing a fascinating and huge topic that has not been encountered in a century. The pursuit of the mystery of the demise of the Guanling biota may reveal a shocking legend.

The appearance of ammonites in the biota is another highlight of the trip to Guanling, because ammonites are a sign of determining geological age. From this, experts inferred that the Guanling biota belongs to The period should be the late Triassic. According to known geological research results, there was a medium-sized extinction event in the late Triassic. The situation suddenly became clear. Could the overall demise of the Guanling biota be the result of that extinction event? ?

However, is it really that simple?

Strange round tail

After returning to Yichang, project leader Chen Xiaohong made the ichthyosaur, the most eye-catching large reptile in the biota, the number one research object. He believes that the answer to the mystery of the demise of the Guanling biota may be found here.

This is a small warehouse dedicated to storing ichthyosaur fossils by the Yichang Geological Survey Institute. There are some ichthyosaur fossil fragments on the ground. Chen Xiaohong plans to conduct decomposition and research on some parts of ichthyosaurs here.

He was quickly attracted by a few fragments, which were the tail parts of the ichthyosaur. The fragment obviously retained only part of the ichthyosaur's tail, but what was very conspicuous was that the tail was thick and round. Chen Xiaohong stared at it in a daze, and an idea suddenly came to him.

Interview: According to the conclusions of the study of paleontological morphological structures, swimming reptiles have experienced an overall trend of lengthening and flattening of tails during their evolution.

But the tail of the ichthyosaur in front of me is round. According to preliminary geological time inference, the Guanling ichthyosaur lived in the late Triassic, which is already the middle stage of the entire ichthyosaur evolution process. According to common sense, its tail should be relatively flat.

Chen Xiaohong couldn't help but make a bold guess. Could this round tail mean that the evolution of Guanling Ichthyosaurus did not conform to the most suitable mode for survival, and would this be related to its demise? Must be contacted?

However, only a small number of ichthyosaur fossils were transported back to the Yichang Institute. Without comparative research on a large number of ichthyosaur fossils, Chen Xiaohong knew that he needed to do more in-depth work.

The research on ammonites and conodonts overturned the original speculation

At this time, the research results of some other members of the team came out. Surprisingly, their results overturned the guesses made by Chen Xiaohong and others during their field survey in Guanling.

Xu Guanghong, an expert on ammonites from the Yichang Institute, has carefully studied all the ammonites brought back from Guanling. Eventually, he zeroed in on two types of ammonites.

On the surface, the two ammonites appear to be the same in shape, color and size. However, in the eyes of ammonite researchers, they are two completely different ammonites.

This kind of ammonite with obvious knob-like protrusions on the edge shocked Xu Guanghong. He realized that the appearance of this kind of ammonite would definitely cause a big shock in the group, because Chen Xiaohong When others were in the field, they had speculated that the demise of the Guanling biota might be the result of the extinction event of medium-sized organisms in the late Triassic. However, the ammonite in Xu Guanghong's hand could completely overturn such speculation.

In order to explain the problem more effectively, Xu Guanghong dug out authoritative ammonite research materials.

Synchronous voice: This is a rough ammonite. Look here. This kind of ammonite shows that it belongs to the Carnian period.

Interview with Xu Guanghong: The rough ammonite indicates that it belongs to the Carnian period...

The Carnian period is a more subtle stage in the Late Triassic, about 220 million years ago Six million years ago, and the known medium-sized biological extinction event occurred in another stage of the Late Triassic - the Norian stage, which was more than 10 million years later than the Carnian stage.

Later, Li Zhihong, an expert who specializes in conodont research, gave the results. Conodonts are extremely tiny tooth fossils of ancient animals. For a long time, the geological community has regarded them as the golden nail that defines the geological era. By crushing the formation rocks and picking out extremely small conodonts under a microscope for identification, the identification results also show that the specific age of the Guanling biota does indeed belong to the Carnian period.

Then, the Guanling biota that lived in the Carnian period was obviously not affected by the biological extinction event that occurred more than 10 million years later. Facts show that it is necessary to find the reason for the demise of the Guanling biota. The reason is that from now on, the original thinking must be changed.

Confused Chen Xiaohong

For a moment, Chen Xiaohong felt a little confused. One of the most gratifying conjectures was proved to be untrue, and the next work was unclear because there were no clues. For several days, he worked day and night in a small warehouse cleaning ichthyosaur fossils. If the rough stones that were brought back were to be used for research, they had to use cleaning tools to separate the fossils from the rocks and expose them. The clear state of the ichthyosaur skeleton.

For Chen Xiaohong, this ichthyosaur among the entire Guanling biota seems to have endless secrets hidden behind each of its bones. It may be able to reveal a bizarre story hundreds of millions of years ago. The story of the extinct kingdom of ancient creatures once happened, but what kind of story would it be? Where is it hidden?

Screenshots from the film

The mystery of the death of the ichthyosaur is even more bizarre

At the same time, other members of the team are also doing research, hoping to learn from it. Some clues were found from different angles to predict the cause of the demise of this biota. However, their work was not smooth. Only Professor Zeng Qingluan, who studied brachiopods, discovered that the living area of ??the Guanling biota actually belonged to a shallow sea area.

Interview with Zeng Qingluan: ...(process it again and find a shot of the arm and foot)

This conclusion once again confused Chen Xiaohong, who studies ichthyosaurs. According to foreign data, Ichthyosaurs are deep-sea animals, so why did so many ichthyosaurs swarm and die in the shallow sea area of ????Guanling? The situation is becoming more and more confusing. The place where the ichthyosaur died is so strange. Is this somehow related to the demise of the entire Guanling biota? Various associations and doubts came one after another, and Chen Xiaohong felt that it was necessary to conduct more in-depth research on ichthyosaurs.

Thoughts brought about by crinoids—research from the environment

At this point in the research, a different viewpoint suddenly emerged. Professor Wang Xiaofeng believes that even if the cause of its own demise is found from the ichthyosaur, it is unlikely to solve the mystery of the death of the entire Guanling biota. He plans to work more on the environment, an idea he came up with while studying crinoid fossils.

During the excavation and research of crinoid fossils, what surprised Wang Xiaofeng most was that there were so many crinoids buried in the Guanling strata, and most of these crinoids were intact. From the roots, stems to crowns, and even the thin barbules on the wrists, they can all be clearly revealed from the fossils.

According to some known research results, after crinoids die in the ocean, they are often quickly washed away by the sea water. Therefore, only with extremely harsh environmental conditions can they be quickly deposited and Be buried, thus forming fossils.

It is hard to imagine what kind of region Guanling was hundreds of millions of years ago, which provided such harsh environmental conditions and preserved such a delicate form of crinoids.

Wang Xiaofeng believes that it must be an extremely special environment, and this special environment must also have some connection with the overall demise of the Guanling biota. Then, perhaps starting from the environment is the right direction.

Strange Ichthyosaurus

At this time, experts who study various categories of organisms are working in the same direction, hoping to find out the reasons for the demise of the Guanling biota from their respective fields. The real reason. Chen Xiaohong felt that the work was gradually getting on track. During his detailed analysis of ichthyosaurs, he also discovered some strange phenomena.

This is an elusive piece. The fragment was part of the tail of the ichthyosaur. What surprised Chen Xiaohong was that the tail vertebrae of this ichthyosaur was actually covered with neural spines that were larger than the tail vertebra itself. This was something he had never seen before. .

Soon, Chen Xiaohong was attracted by another ichthyosaur fossil specimen, which he collected from farmers during his stay in Guanling. It is not that big, and every part from head to toe appears to be very complete.

At first, this specimen made Chen Xiaohong a little excited. The neat and thick neural spines on its vertebrae and the strange combination of the head and neck seemed unusual. Could it mean something like Another case that can surprise the world of paleontology? However, Chen Xiaohong felt more and more that his idea was unreasonable. Experience told him that the specimen in front of him might be just a joke.

When she was in Guanling, Chen Xiaohong had encountered similar jokes. It was an extremely beautiful ichthyosaur fossil collected by the Guanling County government from farmers. It has clear outlines and complete structure. The most surprising thing is that this ichthyosaur has limbs that are completely different from other ichthyosaurs.

(Interview with Chen Xiaohong: Do I think this is...)

However, the hind limbs of this ichthyosaur appear extremely clumsy. If you look closely, they seem to be artificially carved. . Upon closer inspection, although the fossil appears to be a whole, the material reveals that it is not a complete fossil.

Interview: The truth is made up of many dragons.

It turns out that in order to make money, some farmers in Guanling came up with some ways to fake fossils based on their long-term experience in contact with fossils.

Some fossils were incomplete, so they used different fossils to splice them together to create fossils that looked strange but were actually false; some people even carved directly on the rocks. Their practices directly brought doubts and difficulties to geologists studying fossils.

The morphological structure of the ichthyosaur cannot lead to its demise

Chen Xiaohong put aside those confusing and strange fossils and began to conduct detailed research on the decomposition of various parts of the ichthyosaur's body. He believed that certain morphological features associated with death should be found.

This is the head of an ichthyosaur with a length of about 7 or 8 meters. The most conspicuous thing on it is its big eyes. The ichthyosaur's orbit was nearly oval, with its diameter accounting for 16.9% of the total length of the skull, and the skeletal tissues such as the lacrimal bone and front and rear frontal bones that formed the orbit were very developed. This is a pair of eyes that can hunt for food normally under extremely low deep sea light. Such a pair of eyes alone can prove that Guanling Ichthyosaurus, like ichthyosaurs found in other parts of the world, should live in deep sea areas. animals. The question that puzzled Chen Xiaohong was once again activated in his mind by these big eyes: Why does a deep-sea animal rush to the shallow sea area of ????Guanling and never leave until it finally dies?

This was obviously a question for which the answer could not yet be found. Chen Xiaohong could only put it aside temporarily because he soon had new thoughts.

Based on the analysis of the back bones of the ichthyosaur, Chen Xiaohong speculated that the Guanling ichthyosaur had no dorsal fin.

For a swimming animal, the lack of fins on its back is obviously not conducive to maintaining balance during swimming. Combined with the overall body shape of Guanling ichthyosaurs, they are generally huge and have extremely long tails, accounting for almost half of the entire body length. This is obviously not a shape that can dominate swimming.

However, Chen Xiaohong’s research conclusion seems to be limited to this. Although the shape of Guanling Ichthyosaurus is not dominant in swimming, there is no sign that there is anything in their morphological structure that would lead to their demise. Hidden danger.

Interview with Chen Xiaohong: Its morphological structure has not reached the point where it is unsuitable for survival...

The long mouth of the ichthyosaur has uneven teeth like crocodile teeth. This is a type of tooth that is not suitable for chewing.

Interview: Suitable for fast hunting...

How could an ichthyosaur with powerful hunting ability not be suitable for survival?

In addition, there is an obvious discontinuity in the tail skeleton of Guanling Ichthyosaurus.

Interview: I bent down, and the trend of neural spines is wrong...

It can be believed that the ichthyosaurs at this time have already shown an evolutionary trend in the tail. If they evolve according to this trend Going down, its tail, starting from this position, will evolve into a tail fin. Foreign experts have discovered that ichthyosaurs from the Jurassic period did have a tail fin. The origin of this tail fin evolved from the increasingly obvious tail creases of ichthyosaurs.

Combining all the physical elements, this is a marine reptile that looks similar to a fish. It has a pair of big eyes suitable for living in the deep sea, and a long mouth that is easy to catch prey. Its body is in the shape of a fish, with a pair of paddle-shaped front and rear fins on the front and back of its abdomen. The tail, which is nearly half its body length, begins to have a downward curve of the tail vertebrae, indicating that the ichthyosaur will have a tail fin that is more suitable for swimming. .

Everything shows that ichthyosaurs cannot push themselves into a desperate situation because of their own body structure problems.

The research on ichthyosaurs seems to have entered an embarrassing situation: although Chen Xiaohong has been able to restore the general image of the Late Triassic ichthyosaurs based on a large number of complete skeleton fossils of Guanling ichthyosaurs, which makes up for the A huge missing link in the history of dragon research, however, another problem that has troubled the entire research team - the mystery of the demise of the Guanling biota, according to Chen Xiaohong's research, does not seem to be necessarily related to the ichthyosaur itself.

Everything is normal for the ichthyosaur

This is the slicing workshop of the Yichang Institute. The slicing staff is cooperating with Chen Xiaohong to study the feeding habits of the ichthyosaur. The fossils extracted from the stomach of the ichthyosaur were sliced ??and polished here, and finally formed into extremely thin slices of the stomach residue. Through microphotography, the general food structure of the ichthyosaur can be analyzed.

Interview with Chen Xiaohong: The food structure of ichthyosaurs...

It is obvious that there were a large number of creatures that could feed ichthyosaurs in the Guanling area at that time, and the feeding habits of ichthyosaurs were not abnormal. , This shows that the ichthyosaurs in Guanling still maintained a healthy life until the moment of their demise.

Soon, Chen Xiaohong discovered another pregnant ichthyosaur fossil. The belly of this ichthyosaur is far larger than the normal size. Only by careful observation can you see that there are more than ten small spines in its belly, which are the embryonic fossils of unborn small ichthyosaurs.

Normal feeding habits, normal reproduction, and normal physical development and evolution, all of which seem to prove that the ichthyosaurs in the Guanling area lead a leisurely life and are thriving. There is no evidence that the extinction event that occurred hundreds of millions of years ago is related to the ichthyosaurs themselves.

However, this result makes the problem more prominent. Since the ichthyosaurs lived so normally and prosperously, why did they all suddenly die in Guanling?

Paradise of survival and hell of death?

Chen Xiaohong had to go back and think about the question that once made it difficult for him to think about it. How could Guanling, a place that has been proven to be a shallow sea area, gather and perish so many deep-sea animals? ——What about the ichthyosaur? After conducting an overall and detailed study of ichthyosaurs, Chen Xiaohong felt that perhaps something could be gained by starting from this strange place.

Perhaps, Guanling hundreds of millions of years ago was indeed an unimaginably strange place. Its special environment confused a large number of creatures to live and multiply here, and eventually all of them perished in this place. here.

The question is, what kind of place is this special place of death? It turns out to be the paradise of survival and the hell of death!

After several rounds of research, Chen Xiaohong discovered that the research on the mystery of the death of the Guanling biota finally came together, just like Professor Wang Xiaofeng was inspired by crinoids. , the study of ichthyosaurs has inevitably entered the stage of exploring the living environment.

Chen Xiaohong is very clear that in the next step, their main topic will focus on the ancient geological environment of Guanling. What kind of results will this new idea bring them?