Dinosaurs have long been the subject of lots of scrutiny for researchers trying to understand prehistoric life on Earth. One of the questions that remained unanswered for decades is whether these ancient reptiles were cold-blooded or warm-blooded creatures.
But it seems that paleontologists have finally managed to solve this longstanding mystery. As researchers dig deeper into the past of these historical animals, more and more signs are indicating that dinosaurs may have actually had warm blood after all. These clues include metabolic clues in eggshells, as well as the dinosaurs' known ability to withstand freezing temperatures - a skill only warm-blooded creatures are known to have mastered.
However, according to other scientists, a third option might be possible. These researchers hypothesize that dinosaurs were neither ectotherms (cold-blooded creatures) nor endotherms (warm-blooded creatures). Rather, they could be mesotherms - similar to turtles - who, like endotherms, burn internal energy to control their body temperatures, but in a different consistency than mammals and birds do. Thanks to Yale University molecular paleobiologist Jasmina Wiemann, researchers can now use dinosaur fossils to calculate their metabolic rates. "Metabolism is how effectively we convert the oxygen that we breathe into chemical energy that fuels our body," explained Wiemann. In this conversion process, she explains, our bodies create side products that interact with proteins, sugars, and lipids in our bodies. This interaction results in chemically stable waste that acts as a metabolic indicator, telling us what temperatures leftover minerals in the bones formed at.
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Some ornithischians, including Stegosaurus, Triceratops, and a hadrosaur secondarily reduced their metabolic rates to those found in modern ectotherms (i.e., lizards), suggesting thermoregulatory behaviors such as seasonal migration, sun basking, or preferences for warm climates. pic.twitter.com/go7HaIYe9V
— Dr. Jasmina Wiemann (@jasmina_wiemann) May 25, 2022
So, researchers compared breathing waste found in the bones of creatures that roam our planet today to form a scale of waste to metabolic rate. Then they used this scale to calculate an estimate of the metabolism of dinosaurs. According to results, some species' metabolism matched that of cold-blooded animals, while others appeared to be warm-blooded. Findings suggested species like Triceratops and Stegosaurus were ectotherms, while Pterosaurs seemed to be endotherms. "This is really exciting for us as paleontologists – the question of whether dinosaurs were warm- or cold-blooded is one of the oldest questions in paleontology, and now we think we have a consensus that most dinosaurs were warm-blooded," said Wiemann. "We are living in the sixth mass extinction, so it is important for us to understand how modern and extinct animals physiologically responded to previous climate change and environmental perturbations so that the past can inform biodiversity conservation in the present and inform our future actions." We definitely agree.
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