The study reveals when the first warm-blooded dinosaurs walked the Earth

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Were dinosaurs warm-blooded like birds and mammals or cold-blooded like reptiles? It is one of paleontology’s oldest questions, and collecting the answer is important because it shows how prehistoric creatures lived and behaved.

Challenging the prevailing idea that they were all slow lizards, lumbering that basked in the sun to control their body temperature, research in the last thirty years has indicated that some dinosaurs were probably birds, with feathers and possibly the ability to generate body heat itself. .

However, it is difficult to find evidence that shows without doubt what the metabolism of dinosaurs was. Clues from eggshells and dinosaur bones suggest that some dinosaurs were warm-blooded and others were not.

A new study published in the journal Current Biology on Wednesday suggested that three main groups of dinosaurs adapted differently to temperature changes, with the ability to regulate body temperature emerging early in the Jurassic Period about 180 million years ago.

Based on fossils from 1,000 dinosaur species and paleoclimate information, the new study looked at the spread of dinosaurs across different environments on Earth during the age of the dinosaurs, which began about 235 million years ago and ended 66 million years ago ago when an asteroid slammed into Earth.

The research suggested two of the three main groups – meat-eating theropod dinosaurs, including T. rex, and plant-eating ornithischians, of which Triceratops and Stegosaurus were prominent members – lived in cooler climates during the Jurassic Period early. These dinosaurs may have evolved inothermy, or the ability to generate body heat internally, according to the study.

Féachann cuairteoirí ar chnámharlach Triceratops ollmhór atá os cionn 66 milliún bliain d’aois, ainmnithe John More,” on display before being sold at the Drouot auction house in Paris in October 2021. – Sarah Meyssonnier/Reuters” src=”–/YXBwaWQ9aGlnaGxhbmRlcjt3PTk2MDtoPTU0MA- -/”/> “John More,” on display before being sold at the Drouot auction house in Paris in October 2021. – Sarah Meyssonnier/Reuters” src=”–/YXBwaWQ9aGlnaGxhbmRlcjt3PTk2MDtoPTU0MA- -/” class=”caas-img”/>

Two groups of customizable dinosaurs

Therapsids and ornithischians lived in a wide range of thermal landscapes in their respective evolutionary histories and were “remarkably adaptable,” the researchers wrote. Recent fossil discoveries show that different species of dinosaurs even thrived in the Arctic, breeding and living there year-round.

“Warm-blooded animals tend to be more active, for example, cold-blooded animals tend not to build nests,” said lead study author Dr Alfio Alessandro Chiarenza, a Royal Society Newton International Fellow in the Department of Universe at University College London.

In contrast, the tall, plant-eating sauropods kept to warmer regions of lower latitudes, and the availability of richer foliage in certain habitats was not the only reason the study found. The sauropods, including Brontosaurus and Diplodocus, also seemed to thrive in temperate, Savannah-like environments and practiced “long climatic preservation,” the researchers wrote.

“It fits well with what we imagine about its ecology,” Chiarenza said. “They were the largest land animals that ever lived. They would probably overheat if they were warm blooded.”

Besides, he said, the amount of plant material they would have to eat if they were warm-blooded would be unsustainable.

“(These animals) lived in herds and we know that each of them was the equivalent of 10 African elephants. (If they were warm blooded) they would just destroy plants. It makes more sense, as living animals, for them to be more cold-blooded.”

However, Jasmina Wiemann, a postdoctoral research scientist at the Field Museum of Natural History in Chicago, said the results of this study were in contrast to her own research, which looked at molecular traces of oxygen intake found in dinosaur fossils. Their 2022 study suggested that ornithischians were more likely cold-blooded and sauropods warm-blooded.

She questioned how much a dinosaur’s biogeographic range was determined by its metabolic capacity versus other factors such as behavior, growth strategy, diet preferences and other ecological interactions.

“Cold-blooded here are some animals with extremely fast growth rates (ie, sauropods), and by necessity, a fast metabolism, while other animals with very slow growth rates (ie, ceratopsians) are found as endotherms,” Wiemann. said. “Those discrepancies need to be addressed.”

An evolutionary trigger

Chiarenza said the model, developed by researchers at UCL and Universidade de Vigo in Spain, suggested that the earliest dinosaurs were more reptilian and cold-blooded. But a period of global warming as a result of volcanic activity 180 million years ago, known as the Jenkyns Event, may have caused the ability to generate body heat internally to evolve.

“At this time, many new groups of dinosaurs emerged. Endotherms may have been adopted, possibly as a result of this environmental crisis, which enabled the theropods and ornithischians to thrive in colder environments, allowing them to be very active and maintain activity for longer periods , develop and grow faster and produce more offspring,” he added. said in a news release.

As with all model-based research, the study made predictions based on existing information. New fossils or climate information could change that picture. “Of course, if a sauropod turned up in the Arctic that would change,” Chiarenza said.

Paleontologist Anthony Fiorillo, executive director of the New Mexico Museum of Natural History & Science, said the study was “interesting” and the “first real attempt to quantify broad patterns that some of us have thought about before.” Fiorillo, who is also a senior fellow at Southern Methodist University in Dallas, was not involved in the research.

“Their modeling helps strengthen our biogeographical understanding of dinosaurs, and their physiology,” he said.

“This study provides us with a platform to further test what we think we know.”

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