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Researchers have long wondered if dinosaurs were cold-blooded, like the reptiles with which they are categorized, or warm-blooded, like the birds that are believed to be their closest living relatives.
In the latest findings, researchers have proposed that dinosaurs were actually mesotherms, creatures with blood temperatures that come somewhere in between cold- and warm-blooded, Live Science reported.
The study suggests that the dinosaurs fall into a middle category, in a fresh contribution to an enduring debate.
Warm blooded animals, like mammals and birds, need a lot of fuel and use that energy to their advantage, including faster movement and boosted brain power. In burning all that food they also maintain a high, stable body temperature.
Cold blooded animals are more economical, but lack those advantages.
Scientists define these different strategies as “endothermy” (endo for inside; therm for heat) and “ectothermy”.
The study’s first author and a PhD student at the University of New Mexico, John Grady’s paper proposes that dinosaurs may have used a not-too-hot, not-too-cold approach: “mesothermy”.
The evidence for this idea comes from a big survey of the growth rates in 381 different species, including 21 dinosaurs.
Because bones show growth rings much like trees, the size of fossilised dinosaur bones at different ages allows palaeontologists to calculate how fast they put on weight over a lifetime.
So he and his colleagues took growth rate as an indicator of metabolism, and found that dinosaurs occupied a middle ground, somewhere in between modern reptiles and mammals.
Their results also place several living animals with unusual energy habits into the proposed mesothermic category.
Agencies/Canadajournal
