Cold Blooded Dinosaurs: A Literature Review

Grady et al (2014) not only looked at growth rings in fossils, but also sought to estimate their metabolic rates by looking at changes in body size as animals grew from birth to adults.
The researchers compiled an unprecedented dataset on growth and metabolism from studies of hundreds of animals encompassing both extinct and living species, including cold- and warm-blooded creatures, as well as dinosaurs. In general, warm-blooded mammals, that grow about 10 times faster than cold-blooded reptiles, also metabolize about 10 times faster.
When the researchers examined how fast dinosaurs grew, they found that the animals resembled neither mammals nor modern reptiles, and were neither ectotherms nor endotherms. Instead, the researchers coined the
At the same time, dinosaurs' lower metabolic rates compared to mammals allowed them to get by on less food. This may have permitted the enormous bulk that many dinosaur species attained.
All in all, Grady suspected that where direct competition occurs, warm-blooded endotherms suppress mesotherms, mesotherms suppress active but cold-blooded ectotherms, and active ectotherms suppress more lethergic sit-and-wait ectotherms.
When D'Emic (2015) reanalyzed the Grady et al data using different techniques, he concentrated on two different aspects. First, the previous study had scaled yearly growth rates to daily ones as a way of standardizing comparisons; however the growth rates were especially underestimated for larger animals and animals that live in very stressful or seasonal environments.
Thus, doubling dinosaur growth rates, to help them standardize comparisons among animals that are actually not growing for about half the year, on average, and, second, adding birds
(which are known to be warm-blooded and are descendants of dinosaurs) into the calculations, the dinosaurs ended up with growth rates that lends more support that they