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This suggested that archosaurus parents of the Upper Triassic were already warm-blooded, potentially repudiating the origins of endothermy in the family until the Permian, more than 260 million years ago.
"The first crocodyliforms were probably terrestrial and warm-blooded," said Dr. Cubo.
While he is largely in agreement with the research, Dr. Seymour is more interested in whether the first crocodyliforms were properly endothermic.
"Many paleophysiologists are satisfied with the idea of" mesothermal ", which is a state of higher metabolism, but not as high as that of live birds and mammals," he said.
Christopher Brochu, paleontologist at the University of Iowa, is also cautious. It's true that fossils suggest the animals were "Faster on their feet than their living relatives, implying a slightly higher metabolic rate and perhaps a position on the spectrum farther from the cold end than modern crocodilians," he said. declared.
But that may not mean that they were warm to the blood, added Dr. Brochu. The warmer Upper Triassic and Early Jurassic climate may have helped boost the parent metabolism of early crocodile without requiring an entirely endothermic metabolism. Lizards living in hot climates, for example, can easily outperform most of their mammalian predators, as anyone who has ever been hunted can attest.
"The Coldblood and Warmblood categories are not fixed, they are members of a spectrum," said Dr. Brochu. "Some animals are close to one end and others to the other".
During the Mesozoic era, multiple lines of crocodilians returned to water. Among them were behemoths like Deinosuchus who kills dinosaurs, as well as the ancestors of modern crocodiles. According to Dr. Seymour, this transition from predator animals to semi-aquatic ambush is probably the reason why modern crocodiles have adopted a colder lifestyle.
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