A fundamental question in dinosaur evolution is how did dinosaurs adapt to long-term climate changes during the Mesozoic Era (the era of dinosaurs that lasted from 230 million years ago to 66 million years ago) and when did they become independent of their environment? They may have developed bird-like adaptations and become endothermic (warm-temperate). The ability of warm-blooded dinosaurs to thrive in harsher environments, including cold, high-latitude regions, raises interesting questions about the origins of a key innovation shared with modern birds, which is called homeothermia (maintaining a constant body temperature) and endothermic development (producing body heat) played an important role in ecological diversification. Endothermy may have evolved among some dinosaurs during the early Jurassic period, about 180 million years ago, according to a new study.
This artist's impression depicts a dromaeosaurus, a type of feathered theropod, in the snow. Image credit: Davide Bonadonna / Universidade de Vigo / UCL.
In the early 20th century, dinosaurs, like modern reptiles, were thought to be slow-moving, cold-blooded animals that relied on heat from the sun to regulate their body temperature.
The new discovery shows that some dinosaur species were probably able to generate their own body heat, but it is unclear when this adaptation occurred.
In the new study, paleontologist Alfio Alessandro Chiarenza of University College London and his colleagues used 1,000 fossils, contemporary climate models and geography, and the evolutionary tree of dinosaurs to map different climates on Earth throughout the Mesozoic era. We investigated how dinosaurs were spreading.
Researchers found that two of the three major groups of dinosaurs, theropods (e.g. tyrannosaurus and Velociraptor) and ornithischians (including relatives of plant eaters) stegosaurus and triceratops), migrated to colder climates during the Early Jurassic period, suggesting that they may have developed endothermy (the ability to generate heat internally) at this time.
In contrast, sauropods are the other major group that includes: brontosaurus and diplodocuskept in warmer regions of the earth.
Previous research has discovered traits associated with warm-bloodedness in ornithischians and theropods, some of which are known to have feathers or primitive feathers that block internal heat. .
“Our analysis shows that different climate preferences emerged among major dinosaur groups around the time of the Jenkinsian event 183 million years ago, when intense volcanic activity led to global warming and extinction of plant groups. ,” Dr. Chiarenza said.
“Many new dinosaur groups emerged around this time. Perhaps as a result of this environmental crisis, the introduction of endothermy allowed theropods and ornithischians to thrive in colder environments, making them very active.” This may have allowed them to remain active for longer periods of time, develop and grow faster, and produce more offspring.
“Theropods also include birds, and our study suggests that the origin of birds' unique thermoregulation may have been in this early Jurassic period,” said Paleontologist of the University of Vigo. said academic Dr. Sara Varela.
“Sauropods, on the other hand, which remained in warmer climates, grew to enormous sizes during this period. This is also a possible adaptation due to environmental pressures.”
“The lower surface area to volume ratio may mean that these large organisms lose heat at a reduced rate and can remain active longer.”
The study also investigated whether sauropods may have stayed at lower latitudes to feed on the rich foliage unavailable in colder polar regions.
Instead, they found that sauropods seemed to thrive in dry, savannah-like environments, and that sauropods were restricted to warmer climates because of hotter temperatures and more cold-blooded conditions. This supported the idea that it is related to physiological functions.
At that time, the polar regions were warmer and had more vegetation.
The Jenkins phenomenon occurred after lava and volcanic gases erupted from long cracks in the earth's surface and covered large areas of the planet.
“This study suggests that there is a close relationship between climate and the evolution of dinosaurs,” said paleontologist Dr. Juan Cantalapidra of the National Museum of Nature and Science.
“This study sheds new light on how birds inherited unique biological traits from their dinosaur ancestors and the different ways dinosaurs adapted to complex and long-term environmental changes. .”
of findings It was published in the magazine current biology.
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Alfio Alessandro Chiarenza other. Early Jurassic origins of avian endothermy and dinosaur thermophysiological diversity. current biology, published online on May 15, 2024. doi: 10.1016/j.cub.2024.04.051
Source: www.sci.news
