Why can't a creature LOOK like a worm, but have brains like a mammal?
Because it has absolutely nothing to use the intellect on. It doesn't even have limbs. Making it smart wouldn't benefit it as an organism in any way.
Even if it was smart enough to do math, it still can't reasonably pull that cart. Give it a rest. Oh and it'd burrow in soil, not rock. There's nothing to be found in rock even if we pretend it would. Logically, it'd either end up being a surface animal or not burrow in anything at all.
As for the other bit, sure, we can ignore temperature when putting in these lizards of yours but is it worth it? Giant spiders were put in because hey, spiders. Putting in lizards does not fit the same flavor-based rationale as it'd be done only to come up with a flimsy replacement for an existing slot because of an insistence that dwarves hate all that dwells on the surface. Whether it replaces the animal adequately, whether it's fitting for the civ, whether it's flavorful and whether it actually fits canon are all important questions. If you want to counter my query on the viability of a cold-blooded chasing predator underground with the existence of other ridiculous fauna, fine. But don't paint me as a frothing at the mouth moron for bringing it up.
Anyway, I wasn't arguing for giant moles to be "underground dogs" in the first place.
Why'd you bring up their claws then? My bad anyway
If we really want to talk about a replacement for dogs in a burrowing animal, there are burrowing mamalian hunting animals - the weasel family - badgers, wolverines, mongoose, mink, ferret, etc. Selectively bred large, aggressive weasels, badgers, or wolverines require no stretch of the imagination to be dangerous animals.
Badger is a surface animal, it just nests in a hole. Not sure what the overall point is in insisting on things that burrow into soil, even if they otherwise share the same habitat with everything else.
Otherwise, pretty good. Badgers fall short but wolverines are worth consideration. They're about the right size, dwarfy, fast, strong, tough and intelligent. While solitary, domestication might be able to expand on their existing childhood social behavior to make them tolerate each other. Of course, for flavor, males could be made to hate each other when grown up, necessitating discarding or chaining any extra males that are born. Selective breeding would likely skew the sex ratio, cutting down on losses.
Before Pilsu comes in with "they aren't tamable", dogs weren't tamable without thousands of years of breeding, either. Dwarves are fantastic creatures in a fantastic environment, and to demand that they follow "real-life" models of animals is actually far, far less "realistic" than what we are suggesting. Domestic dogs and cows are all man-made species (no cow would survive in the wild) designed for living in human, and it is unrealistic to expect cultures grown in other environments would not do similar things with animals from their own environment.
Well, seeing it's a game where you can tame god damn cockroaches, I'm just going to assume you're trying to pick a fight by this point. Calm down, me shooting down your suggestion is not a personal attack.
Cows haven't changed that much really.
I also think a giant cold-blooded animal would make for a decent pack animal. Something like a giant lizard or a gecko could be size 11 or something, and have a trade capacity along the underground roads (and it would be nice if we could eventually have working deeproads we can carve out for protected dwarven caravans), with perhaps a [speed:1100] as a concession to a slower metabolism.
Not very dwarfy. If nothing better comes up, I'd prefer if they just used muskoxen and lanterns.
since some seem to think it is unusual that a race that lives underground in a world teaming with underground life would have their own kinds of livestock!
Dwarves dig their fortresses underground. That is not something they could have done since the dawn of time seeing as they use picks to chisel their way into rock. Scarce caves have vegetation of any kind, none of them teem with anything but animals using them as shelter. This lost world you speak of does not exist. A few scattered caves with some forests in them would not change their entire culture. Everything we see so far suggests that dwarves do not limit themselves to one world. It would pose unnecessary hurdles to overcome and waste all the grazing lands at their disposal. Dwarves spending their lengthy existence entirely under some rock is a myth conceived by the playerbase with little to support it at this point.