Schools of fish sealed in slates
Fossils serve as historical evidence of biological evolution, and they can help us reveal how species have changed over the course of evolution.
At the same time, it also shows us what the life of the species in that period looked like.
Very classic ammonite fossils
A complete fossil can bring a lot of information to scientists, and in this sense, the fossil is like a photo taken by Polaroid.
However, such fossils are usually unattainable, and even giant creatures such as dinosaurs are difficult to leave complete fossils.
In addition, over time, geological sports will continue to send fossils into the depths of the earth, and the evidence of history will eventually disappear into the depths.
Partial image of a fish stock fossil
Despite this, there are still a few scientists who have been very fortunate to have found complete fossils that have survived.
At the Dinosaur Museum in the Oishi Fossil Gallery at the Mizuda Memorial Hall in Japan, there is a very special collection, it is not a dinosaur, but a fish.
And there was more than one, a school of fish, large and small fish formed a community, about 259.
From the fossils, you can fully see that although these fish have undergone a long period of time, they can still see their eyes, fish bones, and even the fins on their bodies.
The discovery of this fossil treasure was discovered by The Japanese biological behavior researcher Nobuaki Mizumoto, who thought that the museum was simply exhibiting some fossil collections, but he did not expect that there was such a complete biological fossil here.
The complete state of the fossil slab
In addition, judging from the traces left by the fossils, the fish are not disorganized and stored in the fossils.
Instead, they are stored in an orderly state, with schools of fish appearing to be alive throughout the slate.
This is usually very rare, not just because it stores a complete school of fish.
What's more important is that the movement of the fish does not fit in fossils like a camera, or that most fossils exhibit rigid animal forms.
Because many fossils were formed after the animals died, this slate was clearly sealed when the fish were still alive.
"Brothers aren't running yet!"
Mizumoto decided to collaborate with a Japanese fish fossil expert to see if the fish were actually fossilized in the moments before they died.
Back at the museum, they filmed and mapped the location and course of each fish, then tried to simulate their path.
It turned out that the fish in the school did have a law of movement, and these fish seemed to follow two rules in the school:
Avoid bumping into each other while attracting fish farther away, and the location of each fish doesn't seem random either.
But the question is, what is the cause of this phenomenon, and what kind of fish are in the school?
The external shape of individuals in a school of fish
The study of the behavior brought about by fossils
Scientists came to the University of Bristol for further investigations into animal behavior, and they looked for rules of action for live fish by looking for the relative positions of the fish in the photo.
Although the fish are dead, it still does not prevent scientists from recovering them.
It was later shown that the fish was an extinct bony fish belonging to the order Perciformes.
It appeared on Earth around the time of the Eocene, which is 50 million years ago.
Its main distribution is in the giant mountain stream lakes of Wyoming, Colorado and Utah.
Monolithic stone of the perch bony fish
In terms of body size, these fish are very small, generally within 10 centimeters in length, and their bodies are slender, possibly in order to facilitate the reduction of their own resistance to swim in the water.
Their heads are oblong, their eyes are large, and their mouths are high and short, which explains why these fish can still maintain a relatively complete form after all these years.
From a paleoecological point of view, scientists believe that this fish should feed on small insects, zooplankton and other small animals, and have a gregarious nature.
From the structural point of view of the fossils, their fish school structure is very similar to the modern fish school structure, the whole is more or less elliptical, longer in the direction of movement.
Obviously, this is the typical shape of today's shallow fish clusters. Animal behavior analysis believes that the reason why fish stocks adopt such a structure can reduce predators' tendency to attack head-on, so as to prevent predators from tracking them.
In this set of fossil evidence, the differences between individual fish are also highly consistent.
It is worth noting that this fossil attracts the attention of scientists not only because it is rare.
More importantly, it helps scientists analyze animal behavior from fossils and compare ancient biological activity with modern biological activity.
This will lead to the change in the behavior and activities of animals in the process of evolution.
Animal behavior analysis can help scientists understand species
Fish are, to some extent, the ancestors of the vast majority of species.
Over time, they travel from the ocean to land, are environmentally tested, and evolve under the pressure of natural selection, then branching out.
Ultimately constituting today's biological world, the emergence of fish has largely enriched species diversity.
At the same time, the collective movement of groups of animals can arise from simple rules that control the interaction of each individual with its neighbors.
In today's analysis of animal behavior, the behavior of this coordinated group in biological populations, and whether organisms of evolutionary origin or extinction used similar rules, are still poorly understood.
The analysis of fish fossils is actually very rich
Therefore, this fish stock fossil plays an important role in the study of biological behavior.
In the past, scientists have believed that extinct animals have a hard time preserving their group activity, and most of the time it is difficult to excavate related fossils.
Moments in evolutionary history
In the study of fish fossils, the scientists further analyzed the activity status and direction preference of fish stocks.
The results of the simulation showed that most of the fish in this school were moving in the same direction and that all individuals were within the same stack.
This also confirms the animal behavior between schools of fish and fits well with the classic model of shallow fish.
Structural analysis of fish stocks by scientists
In addition, in the attraction of fish schools, scientists have also done relevant analysis.
Mutual movements within schools of fish help them attract each other.
There is no particular difference in size ordering between fish stocks, and in terms of interaction rules, the fossils reflect that they are no different from modern shoal fish stocks.
At the end of the study, and the most crucial question of the entire fossil, how exactly were they sealed?
As mentioned earlier, it is quite demanding to preserve the behavioral activities of animals through fossils.
Scientists also refer to the fossils as "freezing behavior," such as fights between dinosaurs, trilobites moving in line, and insects that are mating.
Similar freezing behavior is common in amber
Similar fossils that have been excavated today suggest that this operation must be buried quickly.
However, it is actually difficult to deduce the whole process, and the reasons for the fish to become fossils are uncertain.
Scientists believe that perhaps their activity in the shoals makes the fish eternal.
Imagine this group of bony fish swimming in the shallows for food or other activities, and when they come to the sand dunes in the shallow waters, suddenly the whole area collapses.
If so, the fish can be preserved intact.
And it only takes a few seconds or minutes to form a new riverbed, and due to the rapid fixation caused by overcooling or overheating, eventually the fish remains in the stone forever.
Simulated behavior of the shoal
The conditions for achieving this situation are very demanding, and if further clarification is needed, scientists believe that the geological activity of this period can not be ignored.
But during the Eocene, the places where they lived had a warm climate and were less prone to sudden overcooling or overheating.
The overall environment of the Eocene was suitable for biological development
Therefore, for the sudden "solidification" of fish, scientists said that they can only expand their brain holes to imagine.
For the study of collective behavior, the analysis and determination of the evolutionary processes that lead to coordinated collective movement may have different interaction rules due to different ecological conditions and historical contingencies.
Think about it
The discovery of this school of fish suggests that perch fish living in Eocene freshwater systems underwent an evolutionary process and perpetuated this behavior, similar to the niche activity of today's shoal carp, cyprinids, and similar species.
Considering that perch orders have been completely extinct in the past, the related research allows scientists to reconstruct the evolutionary process behind it.
In any case, this group of bony fish has been "swimming" in the slate for many centuries, and perhaps they did not think that they were so unlucky on the day they were sealed.
If not all the factors happen to collide together, how can we communicate with modern fish today?