We explain the history of the dinosaurs, their origin, biological context, how they evolved and why they became extinct.
What is the history of dinosaurs?
Dinosaurs are a vast and diverse group of prehistoric animals extinct, which arose in our planet about 231 and 243 million years ago. Its name comes from the Greek deinos, "Terrible", and sauros, "lizard".
Only evidence of its existence remains in the geological fossil record. However, through decades of studying these findings paleontological And thanks to a growing scientific understanding of the physical, chemical and biotic processes of the Earth, we have been able to learn much about the reign of these animals, among which were the greatest vertebrates that have never existed.
The history of the dinosaurs begins at an uncertain point in the Triassic geological period, the initial part of the Mesozoic or Secondary era (from 251 million years ago to approximately 66 million years ago).
In this era, immense changes occurred in the continental distribution of the planet (for example, the separation of the supercontinent Pangea) and therefore in the weather planetary and in biological forms. The dinosaurs, thus, arose in a much warmer world and with a much higher concentration of oxygen in the atmosphere than the current one.
Judging from the evidence in the fossil record, the first dinosaurs were small carnivores bipeds that evolved to have the limbs under the body instead of to the sides, as occurs in the anatomy of their biological precursors: the archosaurs and therapsids surviving the Permian-Triassic mass extinction that wiped out 95% of the life in the planet.
These new little lizards appeared during the first 20 million years of the Triassic. They had an important evolutionary success, probably linked to the other two minor biological extinction events that occurred in that same period, which ended the species previous and opened new biological niches that were occupied by young dinosaurs.
In fact, the final blow to ancient species occurred in the late Triassic, and is known as the Triassic-Jurassic Mass Extinction. This event that marks the formal beginning of the age of dinosaurs: the Jurassic period (201 to 145 million years ago).
During the Jurassic, dinosaurs grew in size and importance. They became the dominant species on the entire planet and spread to all corners of the planet, including the first flying species, precursors of modern birds.
In the Cretaceous period (145 to 66 million years ago), the last and most extensive period of the Mesozoic era, dinosaurs reached their greatest diversity and colonized all of the habitats of the world. To a large extent, this is due to the distancing of the continents, which separated the species geographically and thus broke the evolutionary uniformity of the dinosaurs, that is, they allowed them to take different evolutionary courses.
In this humid and hot period, most of the dinosaurs that we know today and that appear in books and movies emerged: an important variety of aquatic, flying and terrestrial species, with their respective diets. herbivores, carnivorous Y omnivorous. The gigantic long-necked herbivores, the ferocious terrestrial and marine carnivores (such as tyrannosaurs or mosasaurs) are typical of this moment of diversification.
But the Cretaceous period culminated with a new mass extinction event, which ended the reign of the dinosaurs and allowed the appearance of new species, better adapted to the cold and dry world that was to come.
There are no definitive explanations regarding the so-called Cretaceous-Paleogene mass extinction, but one of the most probable points to a cataclysmic event of planetary magnitude, such as the impact of a large meteor in the Gulf of Mexico. Other hypotheses point to large and prolonged Volcanic eruptions or to abrupt and inexplicable climatic changes.
In any case, this mass extinction event wiped out 75% of life on the planet and the vast majority of dinosaur species, both terrestrial, aquatic and flying.
There is fossil evidence that could suggest the survival of some species until the early times of the following era, although there is debate as to whether they are resurfaced by erosion. In any case, no species of dinosaur, adapted to the hot climates of its it was geological, it could have survived the glacial world to come.
On the other hand, the extinction of the dinosaurs marks the beginning of the Cenozoic era and the world more or less as inherited by the mammals and, later, the first Humans.