DALLAS (AP) — Scientists once thought of dinosaurs as slow, cold-blooded creatures. Later research suggested that some could control their body temperature, but when and how this change occurred remained a mystery.
Now, a new study estimates that the first warm blood dinosaurs may have roamed Earth about 180 million years ago, about half the time creatures have been on the planet.
Warm-blooded creatures — including birds, which are descendants of dinosaurs, and humans — maintain a constant body temperature whether the world around them is cold or hot. Cold-blooded animals, including reptiles such as snakes and lizards, rely on external sources to control their temperature: for example, basking in the sun to stay warm.
Knowing when dinosaurs developed their stable internal thermometer could help scientists answer other questions about how they lived, including how active and social they were.
To estimate the origin of the first warm-blooded dinosaurs, researchers analyzed more than 1,000 fossils, climate models and dinosaur family trees. They found that two large groups of dinosaurs – which include Tyrannosaurus rex, velociraptors and Triceratops relatives – migrated to colder areas during the Early Jurassic period, indicating that they may have developed the ability to stay warm. A third crop of dinosaurs, which includes brontosaurus, became trapped in warmer areas.
“If something is capable of living in the Arctic, or in very cold regions, it must have some way of warming up,” said Alfio Allesandro Chiarenza, study author and postdoctoral fellow at University College London.
The research was published Wednesday in the journal Current Biology.
Jasmina Wiemann, a postdoctoral fellow at Chicago’s Field Museum, said locating a dinosaur isn’t the only way to determine whether it was warm-blooded. Research by Wiemann, who was not involved in the latest study, suggests that warm-blooded dinosaurs may have evolved closer to the beginning of their time on Earth, around 250 million years ago.
She said compiling clues from various aspects of dinosaurs’ lives – including their body temperatures and diets – could help scientists paint a clearer picture of when they evolved to be warm-blooded.
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