Throughout our planet's history, few creatures have captured human fascination like the dinosaurs. Those giants that once populated the Earth now fill our screens, books, and even our toy drawers for as long as we can remember. However, after a lifetime living with the memory of dinosaurs, do we know them as much as we think?
Next, on our site we delve into one of the great mysteries of evolution: Why did the dinosaurs become extinct?
When did dinosaurs exist?
We call dinosaurs the reptiles included in the superorder Dinosauria, from the Greek deinos, which means "terrible", and sauros, which translates as "lizard", although we should not confuse dinosaurs with lizards, as they belong to two different reptile categories.
The fossil record indicates that dinosaurs starred in the Mesozoic era, known as the "Age of the Great Reptiles". The oldest dinosaur fossil found to date (a specimen of the species Nyasasaurus parringtoni) is approximately 243 million years old and therefore comes from from the middle Triassic periodAt that time, the current continents were joined together to form a large landmass known as Pangea. The fact that the continents were not separated by the sea allowed the dinosaurs to spread rapidly across the earth's surface. Likewise, the splitting of Pangea into the continental blocks of Laurasia and Gondwana during the Early Jurassic stimulated the diversification of the dinosaurs, giving rise to countless different species.
Classification of dinosaurs
This diversification favored the appearance of dinosaurs with very varied characteristics that have traditionally been classified into two orders according to the orientation of their pelvis:
- Saurischia (Saurischia): individuals included in this category had a vertically oriented pubic ramus. They were divided into two main lineages: theropods (such as Velociraptor or Allosaurus) and sauropods (such as Diplodocus or Brontosaurus).
- Ornithischians (Ornithischia): the pubic branch of the members of this group was oriented diagonally. This order encompasses two main lineages: the thyrophores (such as Stegosaurus or Ankylosaurus) and the cerapods (such as Pachycephalosaurus or Triceratops).
Within these categories, we can find animals with a very variable wingspan, from Compsognatus, the smallest dinosaur discovered to date, similar in size to that of a hen, to the formidable Brachiosaurus, which reached the impressive height of 12 meters.
Dinosaurs also had the most diverse forms of food. Although it is difficult to confirm with certainty the specific diet of each species, it is considered that were mostly herbivores, although there were also several carnivorous dinosaurs, some of which They preyed on other dinosaurs, such as the famous Tyrannosaurus rex. Certain species, such as Baryonyx, also fed on fish. There were those who followed an omnivorous diet, and many did not reject carrion. For more details, do not miss the following article: "Types of dinosaurs that existed".
Although this diversity of life forms made it easy for them to colonize the entire planet throughout the Mesozoic era, the empire of the dinosaurs came to an end with the last throes of the Cretaceous period, 66 million years ago.
Dinosaur Extinction Theories
The extinction of the dinosaurs is for paleontology a puzzle of a thousand pieces and a difficult solution. Did it happen for a single determining cause or was it the result of the disastrous temporal coincidence of several events? Was it a sudden and abrupt process or a prolonged process over time?
The main obstacle in explaining this mysterious phenomenon is the incomplete nature of the fossil record: not all specimens are preserved in the terrestrial substratum, which gives us an imperfect idea of the reality of the epoch. But thanks to the continuous technological progress, during the last decades new data have been revealed that allow us to pose somewhat clearer answers to the question of how did the dinosaurs become extinct
When did the dinosaurs become extinct?
Radioisotope dating places the extinction of the dinosaurs about 66 million years ago So when did the dinosaurs go extinct? During the Late Cretaceousperiod of the Mesozoic era. Our planet was at that time a place of unstable environment, with radical changes in temperature and sea level. These changing climatic conditions could have led to the loss of some key species in the ecosystems of the time, altering the food chains of the individuals that remained.
How dinosaurs became extinct?
This was the scene when the Deccan Steps volcanic eruptions began in India, releasing sulfur and carbon gases in large quantities, increasing global warming and acid rain.
As if this were not enough, the most popular accused of the extinction of the dinosaurs did not take long to arrive: 66 million years ago, the Earth was visited by a asteroid approximately 10 km in diameter, which crashed into what is now called the Yucatan Peninsula in Mexico and left behind the Chicxulub crater, which is 180 kilometers long.
But this huge hole in the earth's surface was not the only thing brought by the meteor: the brutal collision caused a seismic catastrophe that shook the Earth. In addition, the impact zone was rich in sulfates and carbonates, which were released into the atmosphere producing acid rain and temporarily destroying the ozone layer. It is also believed that the dust raised by the cataclysm could have interposed a layer of darkness between the Sun and the Earth, depressing photosynthesis and harming plant species. Vegetative deterioration would have implied the ruin of the herbivorous dinosaurs, which would drag the carnivores with them to the precipice of extinction. So, due to landforms and climate change, the dinosaurs couldn't feed and therefore began to die.
Why did the dinosaurs become extinct?
The information unearthed to date has given rise to countless theories about the extinction of the dinosaurs, as we have seen in the previous section. There are those who attach more importance to the impact of the meteorite as the abrupt cause of the extinction of the dinosaurs; Others believe that the environmental fluctuation and the intense volcanic activity of the time stimulated its gradual disappearance. Proponents of a hybrid hypothesis also stand out: this theory proposes that climatic conditions and raging volcanism drove the slow decline of dinosaur populations, which were already in a vulnerable situation when the meteorite arrived to deliver the coup de grâce.
So what caused the extinction of the dinosaurs? Although we cannot say for sure, the hybrid hypothesis is the most supported theory because it defends that there were several factors that led to the disappearance of the dinosaurs during the late Cretaceous period.
Animals that survived the extinction of the dinosaurs
Although the catastrophe that caused the extinction of the dinosaurs had a global impact, some species of animals managed to survive and develop after the cataclysm. This is the case of some groups of small mammals, such as Kimbetopsalis simmonsae, a species whose individuals are herbivores similar in appearance to beavers. Why did the dinosaurs become extinct and not the mammals? This is because, being smaller, they needed less food and were better able to adapt to their new environment.
They also resisted certain insects, horseshoe crabs or the archaic ancestors of today's crocodiles, sea turtles and sharks. Also, those dinosaur lovers who may be stricken by the thought of never seeing an iguanodon or pterodactyl should remember that these prehistoric creatures never really disappeared: some still live among us. In fact, it is very easy to see them on any given day taking a walk in the countryside or when we rush through the streets of our cities. Although it may seem incredible, we are talking about birds
During the Jurassic period, theropod dinosaurs underwent a long process of evolution, giving rise to different species of archaic birds that coexisted with the rest of the dinosaurs. When the catastrophe of the Cretaceous occurred, some of these original birds managed to survive, evolving and diversifying until reaching our days.
Unfortunately, even these modern dinosaurs are now in decline and the reason for their decline is easy to identify: it is the human impact. The destruction of their respective habitats, the introduction of competing exotic animals, global warming, hunting and poisoning have caused the disappearance of a total of 182 species of birds since the year 1500, while approximately 2000 others suffer some degree of threat.. Our unconsciousness is the accelerated meteor hovering over the planet.
It is said that we are currently witnessing live and direct the sixth great mass extinction. If we want to avoid the disappearance of the last dinosaurs, we have to fight for the conservation of birds and reserve a high degree of respect and admiration for the feathered aeronauts with whom we come across every day: those pigeons, magpies and sparrows that we are so used to see carry on their fragile hollow bones a legacy of giants.
What happened after the extinction of the dinosaurs?
The impact of the meteorite and volcanism favored the generation of seismic phenomena and fires that increased global warming. But later, the rise of dust and ash that darkened the atmosphere and blocked the passage of the sun's rays produced a cooling of the planet This abrupt transition between extreme temperatures triggered the extinction of approximately 75% of the species that inhabited the Earth.
Even so, it didn't take long for life to reappear in this devastated environment. The atmospheric dust layer began to break up, letting in light. Mosses and ferns began to grow on the most affected areas. Aquatic habitats, which had been the least affected, proliferated. The few fauna that had managed to survive the disaster multiplied, evolved and spread throughout the planet. After the fifth mass extinction that wiped out Earth's biodiversity, the world continued to turn.
