Millions of years ago, giant dinosaurs ruled our planet. It is possible that they would still be here if there were not an accident – the asteroid Chiksulub, which fell to the surface of our planet 65 million years ago. According to the results of a recent study, it was he who caused the death of these prehistoric monsters. But who, apart from the dinosaurs, lived on Earth almost 200 million years ago? Eventually, after the asteroid fell, all dinosaurs went extinct, but life on the planet didn't go away. Let's get to know the amazing animals that shared the planet with giant dinosaurs.
When and how did people learn about dinosaurs?
The first extinct dinosaur was first described by scientists in 1824. Discovered nine-meter remains were found near the British town of Woodstock in early 1818. In 1841, the English paleontologist Richard Owen collected and summarized all the information about fossil reptiles known at the time. He called them "dinosaurs", which means "terrible lizards" in Greek.
Shortly afterwards, in 1843, paleontologists in Connecticut (USA) discovered traces of enormously large birds in sand slabs of geological deposits. Compared to this find, the elephant's foot looked very small. Since then, the researchers have been dealing with the question of how big the bird should have been, and have left their mark. The answer, as we know today, is that these traces did not belong to the bird at all. In the Mesozoic era in the history of our planet from the Jurassic period (around 200 million years ago) to the end of the Cretaceous period (around 70 million years ago), “terrible lizards” lived on Earth. Some of them ran like a kangaroo on their hind legs, and the traces they left closely resemble those of modern birds.
Read more on our channel in Yandex.Zen about the ancient giant dinosaurs that have lived on our planet in the past
It turns out that dinosaurs had land, sea and air millions of years ago. Various lizards lived in the coniferous and fern forests of the world. Some flew through the trees and spread their leathery wings, while others the size of chickens ran through the clearings and huge and very slow dinosaurs – brachiosaurs – lived in the swamps. Incidentally, the world's largest skeleton of a Brachiosaurus is in the geological and paleontological museum of the University of Berlin. This giant's bones were discovered on Mount Tendaguru in Africa. The Brachiosaurus reached a height of 11.87 m, a width of 22 m and weighed at least 50,000 kg. The biggest and most scary, however, as we know today, was the Tyrannosaurus Rex. This predator inhabited the area of the modern United States and Canada. The monster reached 10 meters in length and five in height. His measuring jaws were armed with hundreds of sharp and large teeth. If there had been a tyrannosaurus today, it could easily have had a rhino in its mouth.
But when the land, the sky and the oceans were dominated by dinosaurs, where and especially when did the mammals live? According to a study published in the journal Science, the first mammals ran along with dinosaurs across the surface of our planet. According to the researchers, after the terrible dinosaurs went extinct, all other animals came out of the shadows.
Which mammals lived with dinosaurs?
Two scientific articles simultaneously report on individual mammal species as large as modern hamsters. The fossils of these long-extinct relatives of mammals that we know of were discovered in China and analyzed by an international team from the University of Chicago (USA) and the Beijing Natural History Museum (China). After careful study of the shape of the bones, American University paleontologist Jae-Si Luo and his colleagues concluded that agilodocodon and docofossor existed with dinosaurs 160 million years ago.
Externally, these animals resembled modern moles and squirrels. Docofossor lived underground, as his short, broad fingers with two phalanges prove, similar to small shoulder blades. And the spine of this 9-centimeter mammal appears to be particularly suitable for movements in the underground. Agilodocodon became about 14 cm long and lived under trees. Measured by the structure of the limbs and spine, Agilodocodon was perfect for climbing trees. Researchers believe that he didn't have to go to the ground often because he probably ate sage. Such conclusions can be made based on the structure of the animal's teeth, which plant trunks could penetrate. In addition, the researchers emphasized that signs were found in the anatomy of both animals that correspond to the effects of genes found in modern mammals. It is therefore possible that such genetic cocktails were so useful in evolution that they have survived to this day.
The researchers found that the remains suggest that mammals existed in the Jurassic period. It turns out that we are gradually learning that other animals lived in the shadow of the dinosaurs.
But the tiny Docofossor and the Agilodocodon weren't the only mammals that lived in the terrible lizard era. According to the publication Sciencemag, the well-known Australian Echidna and the platypus appeared more than 150 million years ago. They represent a transitional connection between reptiles and other mammals. The Australian echidna is a type of egg-laying mammal that, to say the least, is not as common. The Australian Echidna was first described in 1792 by the zoologist George Shaw, who described the platypus a few years later. However, due to the animal's long trunk, Shaw initially decided that the Australian Echidna is a relative of the anteater. Just 10 years later, the anatomist Edward Home discovered a commonality in Echidna and Platypus – the cloaca into which the intestine, ureter and genital tract open. Based on this feature, one-pass detachment was further identified.
However, one of the most surprising discoveries was made in the summer of 2000, when a team of researchers led by Timothy Row from the University of Texas at Austin accidentally encountered scattered fossil bones between the rocks of the Kayent Formation in northern Arizona. The paleontologists were not initially surprised to find the remains. Only 9 years later, a specialist who was preparing a fossil for the study noticed something surprising: under the remains were tiny teeth and jawbones that were only an inch long. Scientists later found that the remains were owned by the Kayentaterium – an animal that lived on Earth about 185 million years ago. The full-size kayentaterium is the size of a large cat and could therefore be mistaken for a mammal if not for the large jawbone, the large teeth and the lack of ears. Kayentaterium is a cynodont, a member of the group from which mammals come.
The researchers then extracted from the rock the remains of infants from the first mammals or their relatives from the Jurassic period, not just one, but immediately 38. This discovery has thus become one of the most significant in recent decades. According to researchers, Kayentaterium provides important information about which characteristics define mammals and which characteristics were present in their previous relatives. The skeleton of Kayentaterium is in many ways similar to the skeleton of a mammal and at the same time the skeleton of a reptile. The remains of the young indicate that, unlike mammals that spend more time raising offspring, they have become self-sufficient thanks to well-developed bones and teeth.
This knowledge enables scientists to learn more about the evolution of mammals. Fossil remains in different parts of the planet contradict the assumption that the dinosaurs-era mammals were small, unremarkable insectivores that lived in the shadow of giant reptiles.
Who lived on the planet after the death of the dinosaurs?
The death of dinosaurs was good news for mammals, the number of which increased significantly immediately after this event. According to the results of a study published in the journal Nature, the behavior of mammals changed rapidly as our first furry ancestors gradually left their homes not only at night but also during the day. This factor may have an impact on the development of Homo Sapiens.
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Paleontologists and evolutionary biologists have long believed that the ancestors of modern mammals were nocturnal animals. The fact is that most mammals see well in low light. They've also developed a sense of smell and hearing, and still have a mustache (like Vibrissa in cats) that lets them feel what's in front of them – all of these properties are incredibly useful in the dark. Similarly, when mammals went outside during the day, it was a mystery because it is difficult to distinguish behaviors from fossils. Scientists rely on the shape of the eye sockets and nasal cavities to determine what feelings were important for an extinct animal. However, this information can be misleading. However, to understand exactly when our ancestors changed their nightly and daily lifestyles, the scientists examined the daily and nightly habits of more than 2415 species of living mammals and used genetic data to create family trees.
According to a study published in the journal Nature Ecology and Evolution, the first types of ancestors who were active during the day probably lived 65.8 million years ago – only 200,000 years after the mass extinction that destroyed all dinosaurs except birds. For example, the common ancestor of modern camels, hippos, and deer probably changed from a nightly to a daily lifestyle at about the same time. Today's camels are active during the day, while the hippos are active at night and the deer have a mixed lifestyle. In general, the researchers concluded that the animals' daily activity begins with the disappearance of the dinosaurs. The reason for this is of course the fact that going out during the day was too risky.
This is in line with fossil evidence, which clearly shows that the number and type of mammals has increased rapidly after the death of the dinosaurs. The work supports the idea that mammals have conquered more territory and significantly expanded their behavioral repertoire. The researchers also found that modern primates are mostly active during the day and that the primates of primates seemed to be among the first to adopt daily habits. This can cause us and other monkeys to have color vision and a weak sense of smell, and hearing is much better than that of many other mammals. The fall of the asteroid Chiksulub enabled the ancient mammals to change their way of life and occupy the land, sea and water that previously belonged to giant dinosaurs.