While the history of dinosaurs remains a fascinating subject, we now know much more about these creatures that once walked the earth. These impressively large animals lived during a large period of the Mesozoic or Secondary Era, from 250 million to 65 million years before our era. Several hypotheses have been put forward concerning their extinction, but this time we will focus on the phenomena that contributed to their appearance on Earth.
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Dinosaurs were impressive animals that still arouse our curiosity today. It was an English paleontologist named Richard Owen who coined the word “dinosaur” in 1842, referring to very large bones that were similar in appearance to the bones of lizards. The word dinosaur comes from the Greek “Sauros”, which means “lizard/reptile” and “Deino” which means “terribly large”. These giant reptiles had 4 legs located under their body, unlike the legs of lizards which are located on the sides. Researchers have identified nearly 1,000 species of dinosaurs. They also affirm that the Diplodocus and the Tyrannosaurus Rex did not exist at the same time. The first would have become extinct well before the appearance of the Tyrannosaurus.
From the Big Bang to the Age of Dinosaurs
To better understand the origin of the dinosaurs, we must focus on the chronology of evolution from the Big Bang to the era of the first dinosaurs on Earth. So, about 14 billion years ago, the universe was formed after the Big Bang. It is following this explosion that galaxies, stars, planets were formed… The solar system and its planets appeared 10 billion years ago. Our planet was formed a little later, 4.6 billion years ago. This was followed by the appearance of prokaryotic cells, 4 billion years ago, and photosynthesis, 3 billion years ago. It took several millennia for multicellular life to make its way to the appearance of the so-called “simple” animals or Ediacaran fauna, 600 million years ago.
The evolution continued and the more “complex” animals appeared 550 million years ago. Then came fish and proto-amphibians and then land plants. Insects and seeds appeared almost at the same time, 400 million years ago. As for the first amphibians, they lived 360 million years ago. Then came the reptiles, 300 million years ago and finally the famous dinosaurs, about 250 million years ago.
These “terrible lizards” as they are called lived on Earth for almost 200 million years.
When did the first dinosaur appear?
The very first dinosaurs appeared during the Triassic period, after a major biological crisis, 230 million years ago. They were mainly small bipeds and were called theropods. Like the reptiles that preceded them, they were oviparous and therefore laid eggs. The largest dinosaurs during the Triassic period were barely 6 meters long (19 feet): the Prosauropods and the Plataeosaurs. The latter cohabited with the 30 cm (1 foot) high Mesothaurs, the Heterodontosaurs and the Herraraurs. There were also Procompsognathus which were less than 1 meter long and were fond of lizards and insects.
The Jurassic period
200 million years ago, the Jurassic period began and witnessed the evolution of dinosaurs. These reptiles diversified into different species. It was during this period that the dinosaurs called “terribly large” appeared and that the Prosauropods disappeared. The Diplodocus and the Seismosaurus, for example, lived in this period. These animals were particularly large, even compared to their fellow creatures.
Then came the Stegosaurus, which is recognizable by its spiky back. As for the carnivores, they became very serious predators and soon became as impressive as the majority of herbivores. This is notably the case of the Torvosaurus which was 11 meters long, the Carmataure, the Ceratosaurus or the famous Dilophosaurus immortalized in a movie which borrows part of its name from this period of history.
The Jurassic era, which lasted 55 million years, also saw the appearance of the first feathered dinosaurs, including Archaeopteryx. Recent studies in this field lead us to believe that they are the ancestors of birds or cousins of birds.
The Cretaceous period
145 million years ago, the Jurassic period was replaced by the Cretaceous period. Dinosaurs such as Tyrannosaurs cohabited with Triceratops. A sea bird also appeared: the Ichthyomis. It was an excellent swimmer that could not really fly, but had teeth. It was also during the Cretaceous period that Laurasia and Gondwanaland, which had begun to break up in the Jurassic, disappeared to make way for the continents. If you are interested in studying the history of dinosaurs, check out our article on fossilized dinosaur eggs.
The dinosaurs were scattered and species developed on each of the continents. The reign of the dinosaurs ended 65 million years ago, following an immense cataclysm about which there are many hypotheses: meteorite, supervolcano, both. Ammonites, marine reptiles and pterosaurs disappeared during the Cretaceous. Among the dinosaurs and their cousins, only some species of birds survived.
The Paleogene period
According to researchers, not all dinosaurs became extinct during the Cretaceous. Some may have even survived well into the future. The end of the Cretaceous marks the beginning of the Paleogene period, during which giant birds (cousins of the dinosaurs) and mammals began to colonize the Earth. This period lasted 23 million years.
The Neogene period began 23 million years ago and has continued until now, crossed by the ancestors of the present mammals and birds. Did the dinosaurs disappear at this time? No. To this day, ornithologists list over 10,000 species of birds. Most of them are descendants of the dinosaurs that evolved according to the environment. This is the case of the ostrich, the hoazin of South America, or the penguins.
In the course of their evolution, some of them have developed swimming abilities, while others have lost their ability to fly. We can therefore say that these birds are the “dinosaurs of our time”.
How long did a dinosaur live?
The longevity of dinosaurs depends mostly on their size, as those less than 1 meter tall lived six years or less. On the other hand, large dinosaurs had a very good life expectancy. Some could even live up to seventy years. To find out, researchers have based themselves on fossilized bones.
Scientists even go so far as to say that the herbivores lived much longer than the carnivorous dinosaurs. This is explained by the abundance and diversity of food for herbivores at that time. As for the famous Tyrannosaurs which were very large predators, they lived about 30 years. As for the Brontosaurs, which were herbivores weighing more than 30 tons, they could live a very long time, about 80 years.
Could humans have coexisted with Tyrannosaurs?
As a predator, the Tyrannosaurus was feared by its peers. And it’s a good thing humans didn’t live with this animal, because they certainly wouldn’t have been able to survive. Paleontologists estimate its maximum running speed at 29 km per hour. So, unless you were a champion middle-distance runner, humans would have had little chance of escaping it.