WHEN WERE THE LAST DINOSAURS ALIVE?
The extinction of dinosaurs is commonly associated with the fall of a meteorite that caused a huge cataclysm ( giant tsunami, volcanic eruption, earthquake, etc ) that killed all dinosaurs, after which a new era began. So sounds probably the most common version. But if you don't take into account the very cause of their extinction, the second part at least raises a few questions. What if the irreversible cataclysm didn't destroy the dinosaurs all at once? What if the catastrophe has only triggered a long process of extinction and environmental change? What if the dinosaurs disappeared one after the other because they could not adapt to changing conditions? But before looking for the last dinosaur on Earth, it is curious to know how long the reign of the ancient lizards has lasted.
1) How Long Did the Dinosaurs Live on Earth?
The first dinosaurs, the Archosaurs, appeared 230 million years ago. Typical Triassic representatives were Placearias, Plateausaurus, Celophysis, Cynodontium, and Petinosaurus.
During the Jurassic period, when the Earth's climate was moderate, flying lizards (Archaeopteryx, Pterodactyl, Pterosaurs) and large predatory dinosaurs (Stegosaurus, Diplodocus, Anurognate, Allosaurus, Ankylosaurus, and others) appeared. The remains of some of them were found by paleontologists in the Saratov region in Russia.
During the last period of the Mesozoic era on Earth lived giant lizards, many of them reached 5-8 meters in height and 20 meters long. Typical reptiles of the Cretaceous period: Cycliptor, Seismosaurus, Tyrannosaurus, Iguanodon, and Kulazukh.
All "terrible lizards" were completely different: predators and herbivores, small and large, biped, and four-legged. The average life expectancy of dinosaurs of different species also differed. Small representatives lived very little, 20-30 years. Large individuals lived for 2-3 centuries. It is known that large predatory dinosaurs reached sexual maturity only by 40-50 years.
Paleontologists believe that the life expectancy of small species was from one to two decades, and large dinosaurs could live from 200 to 300 years.
Thus, these prehistoric creatures lived safely on the planet in the Mesozoic, namely from the late Triassic to the end of the Cretaceous period. That's about 225 million years ago to 66 million years.
But when did the tipping point occur that killed such massive and well-adapted creatures?
2) Why Did the Dinosaurs Go Extinct?
Dinosaurs disappeared from the face of the Earth about 65 million years ago, at the end of the Cretaceous period. Along with them, marine reptiles (Mosaosaurs and Plesiosaurs) and flying lizards, many shellfish, and algae have died out. A total of 16% of families of marine animals and 18% of families of terrestrial vertebrates died.
According to the most common theory, the 'great extinction' was caused by the impact of an asteroid or comet falling near the Mexican Yucatan Peninsula. This hypothesis was based on the approximate timing of the extinction of most of the extinct dinosaur species and the formation of the Chiksulub crater (it is a trace of the fall of an asteroid about 10 km in size about 65 million years ago).
Some scientists believe that the dinosaurs exterminated the first predatory mammals, destroying clutches of eggs and calves, and could have been influenced by a sharp drop in sea level, a sharp jump in the Earth's magnetic field and other factors.
Advocates of another theory argue that at the time of the meteorite fall, the dinosaurs were already on their way to extinction. The new theory - combined: it does not deny the impact of the asteroid but gives it a secondary role.
According to scientists, the collision of a celestial object with the Earth and the changes that followed only put an end to a process that has long been going on. They compared the rate at which new species appeared and the rate at which existing species of ancient lizards were extinct. As soon as the last parameter is ahead of the first one, extinction begins.
It is also believed that the splitting of the super-continents, climate change, competition with other animals, and so on could have contributed to the slow extinction of dinosaurs: that is, all those factors that are considered under other hypotheses, except for the version about the asteroid fall.
3) Did All Dinosaurs Die at Once?
Some dinosaurs are believed to have died in a monstrous explosion. The rest of the lizards died within a couple of years from the effects of a giant space body falling. This theory says that the dinosaur deaths were fleeting. However, there's great doubt about that.
At least if the majority of ground dinosaurs could have died immediately from the shock wave and the subsequent giant cataclysm (it is believed that about 70% of ground dinosaurs died at the very beginning of the disaster), their water brothers were less fortunate. They suffered a long and painful death in a sulfuric acid solution. Seismic studies have shown that the asteroid that killed them fell into the sea at a much deeper depth than previously thought, and the rocks he raised were rich in sulfuric minerals. The same powerful explosion then evaporated huge amounts of water containing chemical compounds such as sulfates. The huge sulfate cloud formed contributed to the climatic effects of the explosion. The presence of high amounts of sulfate in the atmosphere led to a significant drop in temperature, and the tiniest droplets of sulfuric acid poured into the ground in the form of prolonged acid rain. This killed the surviving dinosaurs.
For example, a significant proportion of land creatures could die within hours or days of impact as a result of carpet bombing of the surface of the earth's crust with fragments of boulders raised to a large surface. They warmed up the air layers heavily, rendering them unsuitable for breathing, and caused firestorms caused by large-scale fires. Sea creatures, on the other hand, were parted from life as a result of gradual changes in the climate and acidity of their habitat. These changes may have had far more serious consequences for living systems than the events that took place on land.
4) Alamosaurus: One of The Last Dinosaur Alive
(Picture source: palaeozoologist.deviantart.com)
In 2011, American paleontologists discovered Alamosaurus remains in New Mexico.
After the research was done, it was possible to establish a lower threshold of bone age - 64.8 million years.
That is, the last dinosaur on Earth died out not earlier than 64.8 million years ago already in the Cenozoic era of the Paleogene period. This is 1,150,000 years later than it was thought! After taking into account the differences in a calculation, it turns out that the found Alamosaurs lived at least 210 000 years after the meteorite fall. On a geological scale, that's a drop in the sea. But for living things, it's a gigantic period. Imagine that after a planetary disaster, giant lizards lived and multiplied for another 210,000 years!
Surprisingly, the Alamosaurus plays the role of "old-timers". The Alamosaurus is an impressively large herbivorous dinosaur of the sauropod family. It could reach 21 meters in length and 30 tons in weight.
The other question is why did the Alamosaurs die out? After the meteorite fell, life came to its senses 30,000 years later. The last dinosaurs survived their darkest days...
30,000 years after the planetary catastrophe, the Alamosaurs had no predators either competitors for food resources: the old giant reptiles are extinct and the new huge mammals, have not yet developed. Simply these giant dinosaurs were no longer adapted to survive on this planet which had become hostile to them and they ended up extinct slowly and gradually.
The Alamosaurus survivors, in the absence of predators and competitors, could have had repopulated North America and give life to new species that would have colonized Earth again. But for some reason, the second dinosaur era did not happen...
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