Were dinosaurs warm-blooded or cold-blooded? One team is scientists looked to growth rates to try and tell:
Annual growth rings in fossils were used to determine growth rates, while metabolic rates were estimated by using changes in body size as an animal grows from birth to adult (known as ontogenetic growth).
“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; in general doubling one’s metabolic rate leads to a doubling in growth rate,” Grady explains.
However, when they examined the growth rates of dinosaurs, although there was some variation in the rate they grew, they had neither the high metabolic rate of mammals and birds, nor the low metabolic rate of reptiles.
“Surprisingly we found that, instead, they occupied the middle energetic ground.”
Now, more than ever, I want a time machine.