What are dinosaurs?
With the term “Dinosaurs” (from the Greek voices deinos, “Terrible”, and sauros, “Lizard”) we refer to a diverse group of prehistoric animals, whose existence we know through the numerous fossils found in the subsoil of almost all regions of the world.
They were the dominant vertebrate animals on our planet for around 135 million years, from their origin in the Triassic period, approximately 243 million years ago, and their sudden, massive extinction at the end of the Cretaceous period, 65 million years ago.
Dinosaurs were sauropsid reptiles of very variable size, from species no larger than a contemporary rodent, to true giants, among which are the most voluminous beings that have ever existed.
In the same way, they populated all available habitats, from the landmass to the deep sea, and even soared through the skies. Thus, it was a highly diversified set of animals, of which around 500 genera and more than a thousand different species are already known.
What were dinosaurs like?
There is evidence of large quadruped dinosaurs, with long necks and long tails, that slowly roamed the earth, feeding on the leaves in the heights of the trees, such as the famous Diplodocus; but also of terrible bipedal predators, with huge and powerful mouths, with serrated teeth, like the Tyrannosaurus; or true living tanks with a body protected by bony plates and spiny tails, such as the Ankylosaurus or the Triceratops.
The immense variety of dinosaur species that existed proliferated and diversified in a world much warmer and more humid than the current one, and throughout a single existing supercontinent, known today as Pangea.
In addition, the oxygen-rich atmosphere of that time favored its growth and allowed its immense proportions. Initially it was thought that they were slow and cold-blooded animals, but findings made since the 1970s point to the opposite: active animals, high metabolisms and rich social interaction.
Since when is its existence known?
The first dinosaur fossils were discovered in the 19th century, before we had a better understanding of the geological history of the planet. The discovery of the remains of these ancient creatures forever revolutionized our understanding of the history of the planet and of life.
The discovery of these fossils showed that the world is much older than previously believed and that extinction is possible, that is, that the animals that accompany us today have not always existed, and that before them there were species that disappeared. This was at the time an important questioning of religious doctrines on the origin of life.
However, the massive and sudden disappearance of dinosaurs is a matter of study by paleontologists and other specialists, and there are different possible explanations for this.
The most famous theory is the one that maintains that a massive space object (such as an asteroid or meteor) impacted with the Earth approximately 65 million years ago, and caused a global climate catastrophe that extinguished not only the dinosaurs but 75% of the existing species.
Today it is known that birds are the only species descended from dinosaurs, judging by the anatomical similarities between prehistoric fossils and many of these current animals.
At the same time, dinosaurs were an important evolutionary step in the rise of prehistoric warm-blooded mammals, of which modern humans are a very remote relative.
References:
- “Expository text” in Wikipedia.
- “Dinosauria” in Wikipedia.
- “The expository text and its functions” in Educ.ar.
- “What is a dinosaur and how does it differ from other prehistoric reptiles” in National Geographic.
- “What are Dinosaurs?” at National History Museum (UK).
What is an expository text?
A expositive text It is a type of writing whose essential mission is to provide the reader, in an objective way, specific and specific information on a specific topic.
It differs from other textual types, such as argumentative text or narrative text, since the expository text does not contain arguments or opinions in favor of a perspective, nor does it contain any kind of story or narrative.
They are texts in which data, observations, textual citations and other resources predominate in order, as the name implies, to expose an aspect of reality to the reader.