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 extinct prehistoric animals, which arose on our planet around 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 study of these paleontological findings 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 largest vertebrates. that have never existed.
The history of dinosaurs begins at an uncertain point in the Triassic geological period, 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 planetary climate and biological forms. Thus, the dinosaurs arose in a world much warmer and with a much higher concentration of oxygen in the atmosphere than the current one.
Judging by the evidence from the fossil record, the first dinosaurs were small bipedal carnivores that evolved to have the extremities 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 ended 95% of life on 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 wiped out previous species 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 (from 201 to 145 million years in the past).
During the Jurassic, dinosaurs grew in size and importance. They became the dominant species on the entire planet and spread to all corners of it, including the first flying species, precursors of today’s birds.
In the Cretaceous period (145 to 66 million years ago), the last and most extensive of the Mesozoic era, dinosaurs reached their greatest diversity and colonized all the world’s habitats. 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 appear in books and movies emerged: an important variety of aquatic, flying and terrestrial species, with their respective herbivorous, carnivorous and omnivorous diets. 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 in a new mass extinction event, ending the reign of the dinosaurs and it 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 abrupt and inexplicable climatic changes.
Either way, this mass extinction event wiped out 75% of life on the planet and with 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 days of the following era, although there is debate as to whether they are remains re-emerged by the action of erosion. In any case, no species of dinosaur, adapted to the warm climates of its geological age, could have survived the glacial world that was coming.
Secondly, the extinction of the dinosaurs marks the beginning of the Cenozoic era and of the world more or less as it was inherited by mammals and, later, by the first humans.