A new study suggests that possibility:
The study’s results: All of the dinosaur material tested fell within the range of modern endotherms. The Maiasaurus sample in particular, say the authors, tested within the range of modern birds at about 44 degrees Celsius (about 111 degrees Fahrenheit). Finding evidence of warm-bloodedness in all major groups of dinosaur suggests that endothermy was an ancestral trait that evolved earlier in the archosaur lineage.
But wait, there’s a twist: The research uncovered something interesting about Troodon. One sample tested at about 38 degrees Celsius (100 degrees Fahreneheit). However, the other two samples, from two different sites, had significantly cooler body temps of around 27-28 degrees Celsius (80-82 degrees Fahrenheit). The lower Troodon temps matched those of fossil mollusks from the same deposits — because mollusks are ectotherms and cannot self-regulate their heat, the temperature in which their shells formed is considered a proxy for the environment’s ambient temperature.Gemma Tarlach, “Fossil Eggshells Suggest All Dinosaurs May Have Been Warm-Blooded” at Discover
Troodon, the researchers suggest, might have been able to switch endothermy (warm-bloodedness) on and off (= heterothermy).
The paper is open access.
If these researchers are right, then mechanisms for warmbloodedness (endothermy) date back much earlier than we used to think. Maybe one hundred million years less for some kind of Darwinian evolution of the trait?
See also: Stasis: When life goes on but evolution does not happen