For years the accepted theory was that dinosaurs were cold blooded, much like modern reptiles today. However, a study then showed that they were neither cold blooded or warm blooded like animals today. However, a paleontologist revisited that study focusing on the metabolism and growth of the dinosaurs. The re-analysis then provided evidence that dinosaurs were actually warm blooded like many of today's modern animals.
Paleontologist Michael D'Emic of Stony Brook University in New York looked at the same data obtained from the dinosaur fossils including the Tyrannosaurus rex. He concluded that the dinosaurs were more similar to the modern mammals instead of the reptiles.
"The main point of my study is that the dinosaurs that have been studied so far were on average as warm-blooded as mammals living today," says D'Emic, who argued that the 2014 study under-estimated dinosaur growth rates and should have analyzed dinosaurs statistically within the same group as today's birds. "The study that I re-analyzed was remarkable for its breadth -- the authors compiled an unprecedented dataset on growth and metabolism from studies of hundreds of living animals."
"Upon re-analysis, it was apparent that dinosaurs weren't just somewhat like living mammals in their physiology -- they fit right within our understanding of what it means to be a 'warm-blooded' mammal."
D'Emic explained that the previous study failed to account that the dinosaurs showed uneven growth. He found that the fossils had rings, similar to tree rings, suggesting slow downs or pauses in growth of the dinosaurs due to season changes or othe stressful situations.
"This is problematic because many animals do not grow continuously throughout the year, generally slowing or pausing growth during colder, drier, or otherwise more stressful seasons," D'Emic says.
The findings, published in the journal Science, provided additional information on the research of the metabolism and growth of dinosaurs. D'Emic hopes that his research will open other opportunities that will explain how and why there were pauses or slowdowns in the growth of dinosaurs. Learning more about these pauses could prove beneficial in the study of bone diseases today that inflict modern species including humans.
However, not everyone agrees with D'Emic's findings. The authors of last year's study on Thursday disputed D'Emic's conclusions. "We disagree with his central criticisms, and we emphasize that all of our original conclusions stand," said University of New Mexico biologist John Grady.
"Comparing dinosaur growth with the observed growth rate of living vertebrates clearly shows that non-avian dinosaurs were mesotherms," added Grady, using the term for an intermediate metabolism.
Will this latest analysis put to rest the true nature of the blood of dinosaurs? Probably not. But it does shed some light on the similarities that even we, as humans, share with these giant creatures that once roamed this Earth.