Dinosaurs were neither warm blooded like mammals and birds nor cold blooded like reptiles and amphibians; they were rather an intermediate class between warm and cold blooded, according to researchers.
Dinosaurs are currently classified as reptiles, and so it is believed that during their time on the planet for about 135 million years, their body temperatures changed with the climate.
Modern reptiles such as snakes and lizards are cold blooded or ectothermic as their body temperatures change with the environment. On the other hand, birds and mammals are warm blooded or endothermic, i.e. they control their own body temperatures, in a way to keep themselves safe.
Scientists, in order to analyze the mystery, developed a new method that examined the growth and metabolism of extinct species. They analyzed the layers of bone deposits in the fossil remains of prehistoric animals. The study revealed the duration taken by animals to grow, according to Live Science.
"Dinosaurs do not fit comfortably into either the cold-blooded or warm-blooded camp - they genuinely explored a middle way," said lead author of the study John Grady, a theoretical ecologist at the University of New Mexico.
The study analyzed 21 species of dinosaur bones, including predators like Allosaurus and Tyrannosaurus, duckbilled Tenontosaurus, long-necked Apatosaurus, and bird-like Troodon along with a swath of mammals and fish, sharks, birds, snakes, lizards and crocodiles.
"Our results showed that dinosaurs had growth and metabolic rates that were actually not characteristic of warm-blooded or even cold-blooded organisms. They did not act like mammals or birds nor did they act like reptiles or fish," Reuters quoted Brian Enquist, evolutionary biologist and ecologist at University of Arizona.
Grady believes that classifying animals as either cold or warm blooded is not limited to dinosaurs. Like dinosaurs, some other animals alive today such as the great white shark, tuna and leatherback sea turtle also do not fit into either of the categories, he added.
"For instance, tuna body temperature declines when they dive into deep, colder waters, but it always stays above the surrounding water. Endotherms can improve their metabolisms to warm up - for instance, we shiver when cold, which generates heat. Mesotherms have adaptations to conserve heat, but they do not burn fat or shiver to warm up. Unlike us, they don't boost their metabolic rate to stay warm," Grady pointed out.
"Gigantotherms are slower to heat up and cool down, but if they rely on external heat sources like the sun, then they are not mesotherms. In general, mesotherms produce more heat than gigantotherms and have different mechanisms for conserving it," explained Grady.
Researchers believe that the findings could help shed light on how warm blooded animals, such as humans evolved. The origins of endothermy in mammals and birds are not clearly understood. Studying the rate of growth of the ancestors of birds and mammals will reveal the deep secrets of these mysterious creatures.