Most dinosaurs are warm-blooded, like birds and mammals, rather than cold-blooded like reptiles, a study shows that provides the first direct measure of their metabolism.
This research is based on a new method that measures the metabolic rate of dinosaurs, i.e., their greater or lesser ability to convert oxygen into energy in order to survive, according to scientists led by paleobiologist Jasmina Wiemann, from California Institute of Technology.
Warm -blooded animals, such as birds or humans, have a high metabolism. They absorb a lot of oxygen needed for making calories, allowing them to maintain their temperature and stay active.
In contrast, cold-blooded ones, like reptiles, have more moderate activity and rely on external conditions to maintain their body temperature. In other words, they do not heat up in the sun for pleasure, but out of necessity.
This dichotomy caused a problem for dinosaur naturalists. Because one of their descendants, the birds, was warm -blooded, while their closest cousins at the time, like crocodiles, were cold -blooded reptiles.
So a resounding study from 2014 even linked dinosaurs to a system … with hot blood. But always by estimating their metabolism by indirect and unreliable methods, taking into account the temperature of formation of minerals in their bones or their rate of bone growth.
The study published in Nature focuses on the basic elements of metabolism, the use of oxygen, and more specifically the study of its traces in the form of labi in the bone.
It leaves a record of how much oxygen a dinosaur breathes, and therefore its metabolic rate.Jasmina Wiemann explained in a press release.
His team applied this non -destructive method, based on infrared spectroscopy, to the femurs of 55 groups of animals, including dinosaurs, to measure. molecular markers (from residues) linked to metabolic rateaccording to researchers.
Result: in two large groups of dinosaurs, ornithischians have cold-blooded specimens, such as triceratops, with a large collar and two impressive horns, or the stegosaurus, with its spine. Massive, but slow -moving herbivores.
On the other hand, the other group, the saurischians, are the most numerous in terms of species and especially of descent, are essentially warm -blooded. To giant herbivores, such as sauropods, and iconic carnivores, such as the tyrannosaurus, or the aptly named velociraptor, made famous by the film Jurassic Park.
This group is most famous for being home to all families of birds, the only descendants of dinosaurs that survived the massive extinction of the species that occurred 65 million years ago.
It is believed that the warm blood and high metabolism of the birds allowed them to survive this catastrophe, due to climate change caused by a giant meteorite.
In the case of dinosaurs, warm blood does not protect them from it, the study notes.
We are experiencing the sixth extinction of speciesaccording to Ms. Wiemann, Therefore, it is important to understand how present and extinct animals respond to past climate changes and environmental disturbances in order to better understand future biodiversity challenges..
Source: Radio-Canada
