T.Rex was WARM-blooded! King of the Dinosaurs had the ability to internally generate heat – and was not cold-blooded like reptiles, study claims

Anyone who grew up watching Jurassic Park might see the Tyrannosaurus Rex as a lumbering, cold-blooded killer.

But even though T.Rex may not have had a friendship, scientists now say the ‘King of the Dinosaurs’ may not have actually been cold-blooded.

An international team of researchers claims that the ability to generate body heat, like modern birds and mammals, may have first emerged 180 million years ago.

They found that two of the main groups of dinosaurs moved to colder climates during the early Jurassic period, suggesting they could warm themselves.

Co-author Dr Juan Cantalapiedra, from the Museo Nacional de Ciencias Naturale in Madrid, says this finding ‘sheds new light on how birds may have inherited a unique biological trait from dinosaur ancestors’.

For most of the 20th century, dinosaurs were still viewed as large, lumbering reptiles.

Scientists believed that dinosaurs needed to warm themselves in the sun, just like lizards and snakes do today.

But much of what scientists have learned about dinosaurs since then challenges these expectations.

In particular, scientists now know that many dinosaurs actually had feathers or proto-feathers that would have had excellent heat resistance.

This suggests that some dinosaurs may have evolved the ability to make their own heat, known as endothermy, making them warm-blooded, like birds and mammals are today.

To unravel the history of how this ability might have developed, scientists compared 1,000 fossils to a model of the prehistoric climate for the place where they were discovered.

Researchers say feathered relatives of the T.Rex and Velociraptor spread to colder regions to survive a climate disaster and developed the ability to regulate their own internal temperatures. This artist’s impression shows a dromaeosaur, a type of feathered theropod, in the snow

This graph shows how many fossils of the three main dinosaur groups have been found in different climates. You can see how the number of Theropods and Ornithischians in cold climates (purple) increases over time

Dinosaurs can be split into three main groups: Theropods such as T.Rex and Velociraptor, Ornithischians, which include relatives of Stegosaurus and Triceratops, and Sauropods such as Diplodocus and Brontosaurus.

The researchers found that Theropods and Ornithischians spread to colder and wetter climates during the Early Jurassic period, while Sauropods remained in warmer regions.

The researchers hypothesize that Theropods and Ornithischians were able to take this step because they had evolved the ability to regulate their own temperature.

First author Dr Alfio Chiarenza, a palaeontologist from UCL, said: ‘Our analyzes show that different climate preferences emerged among the main dinosaur groups around the time of the Jenkyns event 183 million years ago.

‘The adoption of endothermy, perhaps a consequence of this environmental crisis, may have enabled theropods and ornithischians to thrive in colder environments.’

This graph shows the evolution of theropods, the ancestors of modern birds, in relation to the temperature of their habitat. You can see how more dinosaurs adapted to living in colder (lower on the graph) climates during their evolution

The Sauropods, which include dinosaurs like Diplodocus (pictured), persisted in warmer climates and may have grown to their enormous size to help retain heat

The catalyst for this sudden change may have been a mass extinction called the Jenkyns event, in which huge volcanic fissures covered much of the planet in lava and gases.

This caused the Earth’s temperature to suddenly rise, putting many plant and dinosaur species at risk of extinction.

Dr. Chiarenza says endothermy may have allowed dinosaurs like Velociraptor and T.Rex to remain active for longer periods of time, develop faster and have more offspring.

After the Jenkyns event, the sauropods that remained in warmer climates grew to enormous sizes, with dinosaurs such as Diplodocus reaching lengths of 28 meters.

Theropods such as Velociraptor (pictured) are among the earliest ancestors of modern birds. The researchers say this suggests that the warm-blooded nature of birds could have evolved 180 million years ago

The researchers say this is also evidence of the intense pressure on the environment.

Co-author Dr Sara Varela, from the Universidade de Vigo, said: ‘Their smaller surface area to volume ratio would have meant that these larger creatures would lose heat at a slower rate, allowing them to remain active for longer.’

In addition to busting another dinosaur myth, this study may also provide some insight into the evolutionary history of modern animals.

Modern birds are all warm-blooded and can be found everywhere from deserts to the coldest polar regions.

Cold-blooded animals such as lizards and snakes, meanwhile, are still only found in warmer parts of the world.