#also I assume ankylosaurs have VERY high

[swan2swan]

Thinking about Ankylosaurus ovulation and honestly I need more arguments for and against clutch sizes.

[draconesmundi]

Weren’t Some Pseudosuchians potentially warm blooded? Will your dragons be?

Well we don’t have enough evidence to say either way whether they were warm or cold blooded, but we can make conclusions based on their ecology; plenty of fast-moving predators would need thermoregulatory strategies to accommodate for their speedy lifestyle.

With dinosaurs it is easier to say some dinosaurs were warm blooded, because we have the living dinosaurs to prove it’s true, and plenty of non-avian dinosaurs evolved insulation. Even basal dinosaurs have pyncofibres – dino fuzz! – which means dinosaurs we know to be scaly (ankylosaurs, stegosaurs etc.) evolved to be scalier than their fuzzy anscestors. We can assume that all dinosaurs were probably endotherms (temperature mainly controlled by metabolic processes) or mesotherms (temperature somewhat controlled by metabolic processes, but also controlled by other factors, such as environment, behaviour, thermal inertia etc.).

Warm-to-cold bloodedness is on a vast scale from endotherm to ectotherm, with an area of ‘mesotherm’ between the two.

We don’t get as much insulating fuzz in the pseudosuchian family record, many of them had osteoderms like modern crocodiles do. So we know if they produced heat they did nothing to keep it in. We can assume they did produce some heat from metabolic processes because a lot of them had very active niches, and would have needed to keep their muscles warm for chasing prey (unless they were the plant eating pseudosuchians then I guess they didn’t really chase prey much…).

This means that alongside metabolic processes, the pseudosuchians would use things like counter-current blood flow to maintain their temperature (making warm blood from the middle of the body flow right next to cold blood from the peripheral blood vessels, so the warm blood warms up the cooler blood), and they would make use of the warm ambient temperature in the environment (temperatures in the Mesozoic were higher than they are now –  being warmest at the start of the Triassic – like 10 degrees warmer or something crazy - and coolest in the Jurassic at like 2 degrees C warmer).

Modern crocodiles are ectotherms; they lost their endothermy if their ancestors were endotherms, or they simply lost the warm environment that was beneficial to mesotherm ancestors. On the long sliding scale between ectotherm and endotherm, they aren’t the most ectothermic of reptiles; they have vascular and behavioural strategies for dealing with heat, such as a high vascularised tissue on top of their skull (in the frontoparietal fossa – a sort of indent in front of the temporal fenestra – dinosaurs also had this!) that they pump blood into to help them warm up, and basking with their mouths open has they have a highly vascularised palate to cool down.

There is also the joy of thermal inertia; when you are very very big, it is hard to cool down. Big alligators and crocodiles can maintain their body temperature somewhat by virtue of having a low surface area to volume ratio.

So pseudosuchians may have been endothermic, or mesothermic, but for the sake of my dragon book I may try to make my dragons very similar to crocodiles because it is easier to know about thermal strategies in living animals, there is less speculation.

This ask did prompt me to look up pseudosuchian thermal strategies, and I am grateful because now I know that there was a fair bit more metabolic heat generation going on in the extinct crocs, which should help my dragons maybe survive the colder climates, thank you!

Short answer: mesothermic strategies for my dragons, or I may cave and make them fully endothermic.