One common trope, associated with lizardfolk from Castlevania to Overlord, is their weakness to cold. Now, while it is a fun gimmick, it leaves the problem that lizardmen in Overlord are shown to be intelligent and active, which eats energy and that is a headache for ectotherms.
This is where the dreaded square-cube law comes in. Monitor lizards such as komodo dragons and Asian water monitors exhibit intelligence and emotions while also being fairly active. In terms of size, however, the largest known wild specimen was 166 kilograms (with undigested food still inside) and three meters long. Hafþór Júlíus Björnsson is 180-200 kg AND 206 cm in height.
Now, the square-cube law says that as you scale an object to twice its height, its surface area will increase 4-fold and volume 8-fold. That's important because the surface-to-volume ratio determines how fast something can heat up or cool down, and large animals have much more volume than surface, through which heat escapes. Lizardmen like Zaryusu Shasha are comparable to the aforementioned strongman in size, and I intended on having similarly designed lizardfolk.
This could lead to interesting scenarios as lizardfolk would still be vulnerable to prolonged drops in temperature, so Hot-chocolate Man (OC, donut steel4) is still ideal support for them; and larger lizardfolk would be more resilient, while hatchlings and females would be at greater risk.
On an unrelated note: Why would a female lizardfolk have eyelashes? I guess it's explainable with genetic tampering but still weird.
However, this gigantothermy does come at the price that lizardmen must have a lot of volume, which is mostly energy-hungry muscle. Furthermore, I'm not sure if my trick can completely offset the energy demand of a human-like brain. But then again, crocodiles are a thing, and they are well-endowed with fast-glycolytic muscles that let them tail-slap and death-roll you into Hell where you belong.
So, would gigantothermy be able to solve the actually cold-blooded (ectothermic) lizardmen problem, or the muscles needed would consume too much energy (yes, I could add blubbers, but that feels like a bad idea and not as aesthetic, not to mention buoyancy issues)?
Both images are from E621
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