Dinosaurs: The first warm-blooded creatures?

The artist's impression shows a dromaeosaur, a type of feathered theropod, in the snow. This dinosaur group is popularly known as a raptor. A well-known dromaeosaur is Velociraptor, portrayed in the film Jurassic Park. Credit: Davide Bonadonna/Universidade de Vigo/UCL

About 180 million years ago, some dinosaurs may have started regulating their body temperature like modern birds and mammals.

This exciting discovery comes from a study led by researchers from University College London (UCL) and the University of Vigo.

They suggest that these early dinosaurs developed the ability to generate their own body heat during the Early Jurassic period.

In the early 1900s, scientists believed dinosaurs were slow, cold-blooded creatures, similar to today’s reptiles, relying on the sun to keep warm.

However, newer research shows that some dinosaurs were likely warm-blooded, meaning they could produce their own heat. But exactly when this change happened has remained a mystery until now.

The new study, published in the journal Current Biology, examines how dinosaurs spread across different climates during the Mesozoic Era, which lasted from 230 to 66 million years ago.

The researchers analyzed 1,000 dinosaur fossils, climate models, and the geographic conditions of that time, along with dinosaurs’ evolutionary trees.

The research team found that two main groups of dinosaurs—theropods (like T. rex and Velociraptor) and ornithischians (such as Stegosaurus and Triceratops)—moved to colder climates during the Early Jurassic period.

This suggests they may have developed endothermy, the ability to generate heat internally, during this time. In contrast, sauropods (including Brontosaurus and Diplodocus) stayed in warmer regions.

Previous studies had found traits related to warm-bloodedness among theropods and ornithischians, such as feathers or proto-feathers, which helped insulate their internal heat.

Dr. Alfio Alessandro Chiarenza from UCL Earth Sciences, the lead author of the study, explained that the different climate preferences among dinosaur groups emerged around the time of the Jenkyns event, about 183 million years ago.

This event involved intense volcanic activity, leading to global warming and the extinction of many plant species.

New dinosaur groups emerged during this time, and endothermy might have helped theropods and ornithischians thrive in colder environments. This adaptation allowed them to be more active, grow faster, and produce more offspring.

Dr. Sara Varela from the Universidade de Vigo added that birds, which evolved from theropods, might have inherited their unique temperature regulation from their dinosaur ancestors during this period.

Sauropods, which remained in warmer climates, grew to enormous sizes around this time. Their large size helped them retain heat, allowing them to stay active longer.

Researchers also considered whether sauropods stayed in warmer areas to access richer foliage, but they found that sauropods thrived in arid, savanna-like environments. This supports the idea that their preference for warmer climates was due to their physiology.

The Jenkyns event, marked by lava and volcanic gases erupting from long fissures in the Earth’s surface, played a significant role in shaping the environment and dinosaur evolution.

Dr. Juan L. Cantalapiedra from the Museo Nacional de Ciencias Naturales in Madrid emphasized the close connection between climate and dinosaur evolution.

This research provides new insights into how birds might have inherited a unique biological trait from their dinosaur ancestors and how dinosaurs adapted to long-term environmental changes.

The study included contributions from researchers at UCL, the University of Vigo, the University of Bristol, and the Museo Nacional de Ciencias Naturales in Madrid.

Source: University College London.