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Washington (AFP)
Dinosaur species had made the Arctic their permanent home, and probably developed techniques like hibernation or feathers to survive the cold, according to a new study.
The work, published this week in the journal Current Biology, is the result of more than a decade of excavation to extract fossils, and undermines the idea that these reptiles only lived in milder latitudes.
“Some of the new sites discovered in recent years have revealed some amazing things, namely bones and teeth of baby” dinosaurs, senior study author Patrick Druckenmiller of the university told AFP. of the Alaska Museum of the North.
“It’s amazing, because it shows that these dinosaurs weren’t just living in the Arctic, they were able to reproduce there as well,” he continued.
Scientists first discovered dinosaur remains in 1950 in a region long considered too hostile to harbor reptiles.
Two competing hypotheses were then formulated: either the dinosaurs lived there permanently, or they migrated to the Arctic and the Antarctic in order to take advantage of available resources seasonally, and possibly to reproduce there.
This new study is the first to show evidence that at least seven species of dinosaurs were able to breed at these extremely high latitudes – in this case the Prince Creek Formation in Alaska, between 80 and 85 degrees north latitude, dating from the Upper Cretaceous.
Species discovered include hadrosaurids, called duck-billed dinosaurs, horned dinosaurs like ceratopsians, and carnivores like tyrannosaurs.
The team of researchers found small teeth and bones, some of which are only a few millimeters in diameter, belonging to dinosaurs that had just hatched or died just before.
“They have a particular type of texture on their surface and very specific – they are very vascular, and the bones grow very fast, they have a lot of blood vessels running through them,” explained Patrick Druckenmiller.
Unlike other mammals like caribou, whose offspring can travel long distances almost immediately after birth, even the largest dinosaurs gave birth to cubs that would have been unable to cope with migrations of several thousand. of kilometers.
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– Down jacket with feathers –
“We think of dinosaurs in these kinds of tropical environments, but the whole Earth was not like that,” recalls Patrick Druckenmiller.
The Arctic was warmer then than it is today, but conditions were still very demanding.
The annual temperature was around 6 ° C, but much lower temperatures were the order of the day, with snowfall, during the winter months.
This area was probably covered with conifers or ferns.
“We now know that most of the carnivorous dinosaurs that were there probably had feathers,” said Patrick Druckenmiller. “You can think of it as their own down jacket, to help them survive the winter.”
As for the smaller herbivores, researchers believe they would bury themselves underground and hibernate.
And the older ones, with more fat reserves, relied on lower quality twigs and bark to get through the winter.
On the other hand, the fact that dinosaurs stayed in the Arctic all year round is further clue to the idea that dinosaurs were warm-blooded animals, as other recent studies have suggested. They would then represent a point of evolution between cold-blooded reptiles and warm-blooded birds.
Their ability to survive the arctic winter is “the most convincing evidence so far” that they can be added to the list of species capable of thermoregulation, concluded Gregory Erickson of Florida State University and co-author of the study.
© 2021 AFP
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