Dinosaurs neither warm-blooded nor cold-blooded, study says

By Kyle Johnson,

Scientists say that dinosaurs were neither cold-blood or warm-blooded, but rather something in between.

The study was published in the journal Science and was led by University of New Mexico Ph.D. student John Grady, who tried to answer whether dinosaurs were warm-or cold-blooded by examining their metabolism, reports BBC News.

He and the rest of the team examined the growth and metabolism rate of 21 species of dinosaurs, along 360 other animal species. Growth rings in bones helped them to determine how quickly the animals grew and the metabolism rate let them know how quickly they grew in size.

Warm-blooded animals grow quicker than cold-blooded, but require a higher metabolism, with the two processes called endothermy and ectothermy, respectively. Grady, however, found that dinosaurs don't exactly implement either strategy, but rather some intermediate one, which he named "mesothermy."

"We found that growth rate is a good indicator of energy use in living animals. Warm-blooded (endothermic) mammals grow 10 times faster than cold-blooded (ectothermic) reptiles, and metabolise 10 times faster," Grady said, according to Discovery News. "In general doubling one's metabolic rate leads to a doubling in growth rate."

He added, "Surprisingly we found that, instead, they occupied the middle energetic ground." So the team is suggesting that mesothermy be a useable term, one which would be used to also describe some species of sharks, tuna and turtles.

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