When we think of dinosaurs our mind goes to some topics, such as their extinction 66 million years ago or imagining them surrounded by tropical vegetation. Although these topics correspond in part to reality, it is much more complex, encompassing more extinctions and icy periods, as a new theory tells us, that the dinosaurs came to dominate the world thanks to the cold.
The key in the feathers.
Another stereotype about dinosaurs that has been fading is the one that gave them a skin similar to that of reptiles when a good part of them were actually covered by feathers. Some experts consider that the function of these had to do with reproduction, but it is possible that their main function was shelter.
According to a new study published in the journal Science Advancesthe plumage of the dinosaurs would have helped them survive extinction 200 million years ago, during a period of extreme cold that killed more than three quarters of the species of the time.
The world in the Triassic.
The dinosaurs arose in the Triassic period, a period that began about 250 years ago and ended a little over 200 million years ago, with a mass extinction known among other names as the Triassic-Jurassic extinction event.
It was a hot period according to the fossil record, with a concentration of 2,000 parts per million (ppm) of carbon dioxide in the atmosphere. For reference, the concentration of CO2 in the atmosphere has been between 320 ppm in the mid-1960s and 414 ppm today.
However, climate models estimate that there were cooler areas, at least during the winters. The new study has gone further, finding evidence of seasonal ice in high-latitude areas that today correspond to the Junggar Basin in northwestern China.
Triassic dinosaurs.
The Triassic is precisely the era in which the dinosaurs arose, but at that time it was other large reptiles that dominated Pangea, the supercontinent that brought together the emerged land.
The origin of the dinosaurs dates back to just over 230 million years ago, in the tropical zones of Pangea, although some 17 million years later they had already reached the cold zones. The fossil record of the time tells us that the largest dinosaurs were concentrated precisely at the poles, while in the tropical zones (where they coexisted with large reptiles) they were smaller.
Climate change and extinction.
The mass extinction at the end of the Triassic was believed to be caused by a time of great volcanic activity. It caused the disappearance of more than three quarters of the planet’s species, both in the sea and on land. Some species that nested underground, such as the first mammals or turtles, were saved from it. Also dinosaurs, but for different reasons.
Change in the narrative.
Volcanic eruptions would have increased atmospheric CO2 levels even more, which in principle implies a greater greenhouse effect and therefore higher temperatures. However, the study proposes a different and opposite vision, that of a glacial climate change.
The eruptions would not have released only CO2 into the atmosphere but other gases. These would have blocked sunlight from entering the atmosphere, generating a net cooling effect.
An evolutionary step.
From these survivors arose most of the dinosaurs that survive today in popular culture and those that survive in a literal sense, the birds. These survivors were, yes, a varied group, which included the family (the order) of the pterosaurs; ornithischians, from which the stegosaurus would derive in the Jurassic; the sauropodomorphs, the largest of the group, which would grow (and a lot) until they became the mammoth diplodocus; in addition to the only group that would survive the Cretaceous extinction, the theropods.
Theropods were a group that had, according to the study, a diversity of protofeathers. The group ranges from the tyrannosaurus to the penguins, through velociraptors and all modern birds.
Rediscover the past.
Dinosaurs, as we popularly know them, that is, excluding birds, dominated the world for millions of years, but we know relatively little about them and their environment. Proof of this are the new discoveries that are emerging and that go beyond the fossil finds of new species.
Image | larry felder
George is Digismak’s reported cum editor with 13 years of experience in Journalism