A new study suggests that in the early years of the Jurassic period, dinosaurs may have evolved the ability to regulate body temperature, which modern mammals and birds also exhibit.
Endothermy Among Dinosaurs
All animals tend to thermoregulate in different ways. Both external and internal conditions affect their internal environment. Land animals thermoregulate by moving to a warmer or colder place, exercising to generate body heat, or sweating to lose it.
In the early 20th century, dinosaurs were portrayed as slow-moving, cold-blooded animals that depended on heat from the sun to regulate their body temperature, like modern-day reptiles. However, recent discoveries indicate that some types of dinosaurs could generate and regulate their body temperature, an ability known as endothermy.
Endothermy refers to maintaining a high and relatively constant internal body temperature, with a high metabolic rate at rest as the principal heat source. Modern mammals and birds have a high metabolism and are classified as endotherms. It was assumed that dinosaurs adapted to this behavior at some point, but it remains a mystery when this evolutionary adaptation occurred.
Climate-Driven Evolution
In a new study entitled "Early Jurassic origin of avian endothermy and thermophysiological diversity in dinosaurs," a team of researchers investigated the spread of dinosaurs across different climates on Earth from 230 to 66 million years ago (the Mesozoic era). The experts from University College London focused on 1,000 fossils, dinosaur evolutionary trees, climate models, and the geography of the period.
It was found that two of the three main groups of dinosaurs, theropods, and ornithischians, moved to colder climates during the Early Jurassic period. Theropods include T. rex and Velociraptor, while ornithischians include relatives of plant-eating Triceratops and Stegosaurus.
This suggests that they may have adapted endothermy at this time in history. Meanwhile, sauropods kept to warmer areas of the Earth.
According to first author Dr. Alfio Alessandro Chiarenza, their analyses indicate that different climate preferences emerged among the main groups of dinosaurs around 183 million years ago. This was the time in Earth's history when intense volcanic activity caused global warming and plant extinction.
During this time, many groups of dinosaurs emerged. Endothermy may have been adapted as a result of the environmental crisis, allowing theropods and ornithischians to survive colder environments. This event also enabled them to be highly active and sustain activity over extended periods to grow faster and produce more offspring.
Research co-author Dr. Sara Varela noted that theropods also include birds and their study also suggests that the unique temperature regulation of birds may have its origin in the Early Jurassic epoch. On the other hand, sauropods stayed in warmer environments as they grew around to a gigantic size. Their smaller volume-to-surface area ratio indicates that these large creatures would lose body heat at a lower rate, enabling them to stay active longer.
The research team also investigated whether sauropods might have remained at lower latitudes to consume richer foliage that was not available in colder polar regions. Instead, it was found that these animals thrived in arid environments. This supports that their limits to warmer climates were related to higher temperatures and more cold-blooded physiology.
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