Dinosaurs were mostly warm-blooded animals, such as birds and mammals, unlike reptiles, which are cold-blooded, revealed a study published this Wednesday (25) in the scientific journal Nature.
The study used a new technique for measuring metabolism, that is, the ability to transform oxygen into the energy needed for life, said the scientists, led by paleobiologist Jasmina Wiemann of the California Institute of Technology.
Warm-blooded animals, like birds and humans, have a high metabolism. They absorb a lot of oxygen, which is necessary for the production of calories that allow them to generate heat and remain active.
Cold-blooded animals such as reptiles, on the other hand, have a more moderate activity and the maintenance of their body temperature depends on external conditions. They do not get the sun for pleasure, but out of necessity.
Dinosaur metabolism has always been a dilemma, as birds, which are their descendants, are warm-blooded, but their close cousins, the crocodiles, are cold-blooded.
In 2014, a study even defined dinosaurs as warm-blooded animals. But metabolism measurements have always been made by indirect and unreliable means.
The research published in Nature, on the other hand, directly examines the use of oxygen and, in particular, its bone traces.
These are “remains” that “record the amount of oxygen that a dinosaur breathed and therefore its metabolism,” explained Wiemann.
mass extinction
The researchers applied this non-destructive method, based on infrared spectroscopy, to the femurs of 55 groups of animals, including dinosaurs, to measure “the molecular markers [dos restos] linked to metabolic rates,” said Wiemann.
Observations demonstrated that ornithischians had cold-blooded specimens, such as triceratops, with their protective “collar” and imposing horns.
The other group of dinosaurs, the saurischians —the most numerous in terms of their number of species and above all because of their descendants— was, on the contrary, warm-blooded.
This group includes some giant herbivores, such as sauropods, and very popular carnivores, such as the tyrannosaur or the velociraptor, which rose to fame in the movie “Jurassic Park – Parque dos Dinossauros”.
From the saurischians come all the lineages of birds, the only descendants of the dinosaurs that survived the great extinction of the species that occurred 65 million years ago.
At some point, it was hypothesized that warm blood and metabolism would have been the key for the birds to have managed to overcome the climatic catastrophe caused by the impact of a large asteroid.
According to the study, these factors were not, however, of any help to the dinosaurs.
“We are experiencing the sixth species extinction, and therefore it is important to understand how current and extinct animals responded to climate change and environmental disturbances,” she wrote.
This understanding can be useful in tackling upcoming biodiversity challenges.
