— Scientists have recently confirmed the theory that Spinosaurus, a dinosaur that lived in what is now North Africa, had dense bones that allowed it to dive to great depths and hunt large fish. What else is known about the habits, hunting methods and appearance of this animal?
— Spinosaurus is known to paleontologists only from found fragments of skeletons; in total, fragments of the remains of 26 individuals of such dinosaurs were discovered in the world.
Then, using these fragments, scientists put together the appearance of an extinct animal, like a puzzle.
However, the appearance can be reconstructed in different ways, so data on this dinosaur varies greatly among different researchers.
Thus, it is known that Spinosaurus had bony outgrowths on its back more than one and a half meters high.
Some researchers believe that during the life of the animal these outgrowths looked like spikes, while others looked like a bone “sail” - between the spikes there was a leather membrane equipped with blood vessels.
Still others think that it was not a sail, but a hump.
According to supporters of this hypothesis, Spinosaurus lived in an environment where it could not feed evenly throughout the year.
Therefore, in seasons when there was plenty of food, he stored fat for future use, like a camel.
Spinosaurus - reconstruction
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© Hauke-Christian Dittrich
Judging by the structure of its teeth, Spinosaurus was an omnivorous predator.
He could hunt both large land organisms and catch fish.
— Another large dinosaur, the Tyrannosaurus rex, could have been much larger than previously thought, Canadian scientists came to this conclusion in 2022. According to their estimates, the T. rex could weigh up to 15 tons. Do you agree with these conclusions? What other hypotheses are there in this regard?
— The largest remains of a Tyrannosaurus rex ever found are the bones of a female T. rex named Sue.
Scientists estimate its weight to be about 8-9 tons.
The mechanical properties of dinosaur bones allowed the skeleton to withstand the weight of the animal so that the skeleton did not collapse under the weight of its own body.
It is believed that tyrannosaurs were quite mobile creatures, however, if their weight exceeded 10 tons, then most likely their motor functions would have been limited.
It all depends on the approach to reconstructing the appearance, as in the case of Spinosaurus.
The biomechanics of an animal depends largely on its physiology, and we know little about the physiology of dinosaurs, so we are left with different options.
Reconstruction of the appearance of a tyrannosaurus
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© IMAGO / Frederic Kern
— Why could such colossal land predators exist in the era of dinosaurs? And why are modern predators, with the exception of predatory cetaceans, much smaller than the largest dinosaurs?
- It is assumed that dinosaurs had a rather slow metabolism and were less mobile than modern land predators.
If a lioness, for example, can run long distances in search of an antelope, then the prehistoric predator most likely did not do this.
Therefore, a predatory dinosaur could eat a lot, but after eating, it remained full for a very long time.
If, for example, a wolf had to eat about once a day, then a tyrannosaurus could eat once a month.
— What problems do researchers most often encounter when studying dinosaur remains?
— The main problem is the lack of information.
As a rule, scientists find individual dinosaur bones, or even bone fragments.
Therefore, it is difficult to establish which dinosaur a particular bone belongs to and where it was located in the skeleton.
A gift of fate for scientists is the discovery of a more or less complete skeleton, or at least a skull, as the most informative part of the skeleton.
— As we understand, it is very difficult to determine the sex of dinosaurs. Only a few individuals are known whose gender has been determined. Why?
“Many dinosaurs certainly exhibited sexual dimorphism.
However, in modern animals it often consists of different colors of males and females and their different behavior.
It is clear that we cannot determine these features in the fossil state.
Many modern animals are characterized by different sizes in males and females.
But in some cases, males are larger and heavier than females, in other cases - vice versa.
But there were cases of detection of females.
Their sex was determined because they were found with fully formed but unlaid eggs.
— Previously, Russian scientists assumed that the remains of a miniature theropod dinosaur, Alvarezsaurus, found in Mongolia belonged to an adult animal, but it turned out that it was an individual less than one year old. Why is it difficult to determine the age of an individual at the time of death in dinosaur remains?
“Here we are faced with the same problem of lack of data.
However, the problem of methodology also arises here.
Theoretically, animal bones form seasonal rings, like those on a tree.
When there is a lot of food, bones grow quickly, when there is little, growth slows down.
However, all these characteristic features are not always reflected in the fossil remains of dinosaurs, and there are simply no modern analogues with which to compare.
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©Marla Brose
— When did they start studying dinosaurs and conducting full-scale research? How much has the image of prehistoric dinosaurs changed in connection with new data? Are their images depicted in popular culture (films, books) accurate?
— Full-scale research into the study of dinosaur remains began in the 19th century.
Previously, scientists had found various fossils, but could not determine which organisms they belonged to.
In the 19th century, it became clear that these were the remains of animals different from modern ones, and such bones and fragments began to be searched for purposefully.
As for the appearance of dinosaurs, people’s ideas about it have changed over time and continue to change.
For example, the image of one of the most famous lizards, the iguanodon, so named because its teeth were similar in shape to the teeth of a modern iguana, has undergone significant changes over the years.
At first it was depicted as a reptile crocodile-like lizard, based on the shape of the bone fragments found.
In 1878, several complete skeletons of this dinosaur were found in Belgium, and it turned out that when trying to assemble a skeleton resembling a crocodile, the bones came out of their joints.
Scientists have concluded that the iguanodon walked on two legs and rested on its tail, like a kangaroo.
But when, half a century later, biomechanical research was carried out, it turned out that the dinosaur’s tail has such a structure that it is simply impossible to lean on it.
Now the iguanodon is depicted walking on four legs, with its tail raised above the ground.
How it really happened is unknown, but if humanity ever invents a time machine, then we will find out for sure.
Iguanodon skeleton
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© Bruno Levesque
- It is known that dinosaur remains are found all over the world - in China and Mongolia, in Europe, the USA and even in Antarctica. However, there is very little information about Russian dinosaurs. Did prehistoric lizards even live on the territory of modern Russia? If so, which ones, and where are their fossils most often found?
— Basically, the remains of dinosaurs are found in desert, semi-desert and highly dissected mountainous areas, where there are extensive geological outcrops - outcrops to the surface of rocks.
Most of Russia's territory is covered with forests.
Therefore, finding dinosaur bones in our country is a great success.
In addition, the most densely populated European part of Russia during the Jurassic and Cretaceous periods (from 200 to 60 million years ago), when dinosaurs lived, was shallow seas with individual islands.
Therefore, the conditions for preserving the remains of prehistoric dinosaurs were very unfavorable.
However, dinosaurs still lived in Russia.
Most of the finds are made in the region of southern Siberia.
When road construction and landscaping began in this area, artificial outcrops associated with human activity appeared, and quite a lot of dinosaur remains were discovered.
Fragments are found in the Far East on the banks of the Amur River in the Khabarovsk region, where the first Russian dinosaur, the Amurosaurus, was found.
Reconstructed skeleton of Psittacosaurus sibirica
© Paleontological Institute named after.
A.A. Borisyak RAS
Most of all - about 40 specimens - the bones of the Siberian Psittacosaurus were discovered.
Presumably, representatives of this species weighed up to 29 kg, and their body length reached 170–185 cm. Various duck-billed dinosaurs, species from the group of sauropods - giant four-legged dinosaurs with a small skull compared to the overall size, a massive body and a long neck - were also discovered.
- A recent study found that dinosaurs and pterosaurs had high metabolic rates, which suggests they were warm-blooded. To what extent is this a proven point of view, or is there still disagreement in the scientific community on this issue? Why were dinosaurs considered cold-blooded animals for a long time?
— It was previously believed that the closest relatives of dinosaurs were reptiles.
However, when paleontologists began to study not only bones, but also prehistoric imprints of nerves and blood vessels, they saw a striking picture - the nervous system of some dinosaurs was more complex than that of reptiles and resembled the nervous system of birds.
Moreover, the holes in the bones for blood vessels in such dinosaurs were noticeably larger than required by the physiology of a reptile.
This could only be explained by the fact that some prehistoric animals were more active and warm-blooded.
Physiologically they were closer to birds than to reptiles.
Most likely, dinosaurs were a collection of organisms that were not very related to each other.
Among them were warm-blooded, cold-blooded, and species with intermediate physiology - mesotherms.
— Scientists have been looking for an answer to the question about the reasons for the mass death of a huge number of dinosaurs for decades. The main hypothesis is the fall of an asteroid. However, there are others. For example, that dinosaurs began to die out gradually, long before the disaster. Please tell us more about these theories.
- None of the existing hypotheses provides answers to all questions about the causes of extinction.
Yes, indeed, approximately 66 million years ago an asteroid fell to Earth, forming the Chicxulub crater in the sea and on the coast of modern Mexico.
But it is possible that the meteorite was just the straw that broke the camel’s back; the disaster simply finished off already extinct species.
If it was previously believed that dinosaurs were thriving at the time of the meteorite fall, then according to new data, their species diversity and numbers had already declined significantly during that period.
There are different assumptions regarding the reasons for this extinction.
According to one, for example, in the Late Cretaceous, angiosperm flowering plants began to appear capable of producing alkaloids, substances similar to poisons that protect them from pests.
Herbivorous dinosaurs were unable to adapt to these poisons, their populations declined, and at the same time the number of predators.
According to another version, by the time the meteorite fell, dinosaurs were at an evolutionary dead end - they had lost the ability to adapt to changing conditions.
They simply had nowhere to evolve, so they could not survive the environmental disaster.
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Another reason could be the gradual cooling that began on the planet about 10 million years before the meteorite fell.
Ecosystems met the catastrophe being already unstable and dying out.
— To what extent has science studied dinosaurs to date, and to what extent does the history of their evolution, diversity of species, etc. remain a mystery? How much remains to be discovered by scientists, and do they have new technical tools for this?
— Today, 4 thousand species of dinosaurs have been scientifically described, but complete skeletons have been found for only a hundred species.
Therefore, dinosaurs are a big mystery to science.
Of course, new technologies can help and indeed help in the study of prehistoric species.
For example, mathematical modeling made it possible to answer the question of why representatives of different species and genera of sauropods lived in a small area.
It turned out that they had different food specializations - some could strongly bend their necks to reach plants at the bottom of the reservoir while standing on land.
Others, on the contrary, had difficulty bending down just to drink water.
But their neck allowed them to eat vegetation, trees and bushes.
Scientists still have a lot to study.
Perhaps if we understand how dinosaurs evolved, we can better understand the evolution of humans and other modern species, as well as their future.