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There are some intermediate, mesothermic species that exist today, the authors point out: Animals such as tuna and the leatherback turtle are able to somewhat regulate their internal temperatures, though not to the extent that warm-blooded animals do. The scientists aptly called them “mesotherms” (“meso” basically means “middle” in Greek.) The dinosaurs seemed to sit right in the middle, overlapping with some endothermic and some ectothermic animals. Sure enough, they found that high growth rates seemed to match up with the higher metabolisms of warm-blooded animals, whereas lower growth rates were linked to the lower metabolic rates of cold-blooded animals. And higher metabolisms would probably tend to be endothermic, warm-blooded systems. The idea was that the higher the growth rate, the higher the animal’s rate of metabolism would probably be. They compared the growth rate, adult size and metabolism of 381 vertebrate species, living and extinct, including 21 dinosaur species.
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Was it possible the creatures were actually endothermic?įor this paper, the scientists decided to perform a metabolic census of sorts. Keeping the body’s internal temperature high requires a lot of energy, but it also means mammals can be more active and grow faster.īut researchers have examined dinosaur bones and found signs of surprisingly fast growth – which shouldn’t be achievable with an ectothermic animal because it requires so much energy. Mammals, on the other hand, are endothermic (or warm-blooded), in that we’re able to regulate our own temperature from within. That’s why many reptiles tend to turn sluggish in cold weather. Researchers have long thought the ancient lizard-like beasts were ectothermic (colloquially referred to as cold-blooded) – that is, they rely on the temperature outside of their bodies to help regulate their internal temperature. The new findings in the journal Science hint that dinosaurs’ metabolic systems might be far more complicated than previously thought. New research out of the University of New Mexico in Albuquerque, however, shows that these long-dead creatures may have been a little bit of both. Dinosaurs have long been thought of as slow, lumbering, cold-blooded animals, akin to reptiles like the crocodile and the lizard – but there’s been increasing signs in recent years that they may have been warm-blooded, as mammals and birds are.