So, as the title suggests, I have a reptilian alien species capable of human-tier thought. Anatomically, they are centaur-like (four legs on the ground, two manipulating limbs up top), standing slightly taller than humans and having roughly twice the body mass. I imagine that these creatures would need a good amount of energy to maintain human-level intelligence and support a human-like society, so they are omnivores; their lower body is of a canine build, letting them run fast enough to hunt large prey animals in packs. I presume that all this energy expenditure can only be supported by a warm-blooded metabolism, but this is where I ask my first question: am I wrong in this assumption? Is it feasible for a cold-blooded sapient species to exist? If you think it is, please shoot me your ideas, because I'm very curious.
My second question is less about sapience than it is about thermodynamics. Can a warm-blooded creature reasonably evolve without requiring feathers or fur to maintain its body temperature? I don't think it's a coincidence that mammals and birds, the two living classes of vertebrates that are warm-blooded, are also the ones with a coat that can either insulate or ventilate as appropriate.
My (warm-blooded?) sapient species is scaly. No coat. Right now I'm imagining that their scales either (1) are very thick/insulating on their own or (2) tessellate together in a way that traps a layer of tiny air pockets. Since this scale layer can't vent itself in case of overheating the way fur or feathers can, they have a "mane" of fleshy tentacles on their heads that are completely scale-free and act as heat sinks. If any of these mechanisms are insufficient, lacking, over the top, or otherwise incorrect--for example, should the heat sink tentacles sweat?--I would love to hear your suggestions for improving them!