@datarama these are cool facts! The monitor lizard one really surprises me, because birds and reptiles are somewhat closely related in the grand scheme of things, and I thought bird respiration actually depended (at least at peak capacity) on the motion of the flight cycle exerting pressure on their multiple sets of lungs in sequence.
@MaddieM4 In the grander scheme of things we'd probably have to classify birds as a kind of reptile. If crocodiles and lizards are both reptiles then so are birds: Crocodiles are more closely related to birds than they are to lizards.
Anyway, the problem with breathing while moving is specific to lizards and tuataras. The phenomenon is called Carrier's Constraint (after a paleontologist who documented it in prehistoric animals): Animals that flex their bodies side-to-side while moving are going to constantly compress one lung while expanding the other, pushing stale air back and forth between lungs rather than expelling it. It doesn't help that most lizards don't have dedicated respiratory muscles - given the aforementioned constraint, they wouldn't actually help much.
Other reptiles don't have this problem: Turtles don't flex their bodies at all (and breathe using a sling-like muscle wrapped around their lung - obviously, they can't expand and contract their chests!), snakes only have one lung, and archosaurs (crocodilians and birds) have unidirectional lungs - air travels in a single continuous loop through their lungs and out again, rather than sloshing back and forth into a bunch of "dead-ends" like in mammal (or lizard) lungs. Birds use air sacs both to pump and to keep stale and fresh air separated; crocodiles use valves and muscles*. It's a pretty sophisticated system, arguably more advanced than what we mammals have.
Monitors are lizards, and move like lizards - but they've solved the problem by evolving a large bellows-like pump in their throats, with which they can force fresh air into their lungs (which then expels stale air). They've also separately evolved a variant of the "looping" structure of archosaur respiration.
Some agamids and iguanids have a pragmatic quick-fix: They'll get up on their hindlegs and run bipedally, which avoids the side-to-side flexing.
@datarama THAT'S why they run on their hind legs? Dang! Also, I feel like I better understand why most lizards run so fast, but in short bursts, like the blue-bellies we used to catch as kids. If I had to hold my breath, I'd stick to brief sprints too.
I am very much enjoying having a lizard expert in my social circle 😁
@MaddieM4 Yup. Most lizards (present company excluded) are very strong sprinters - but have very little stamina.
@MaddieM4 In fairness, I guess I should mention that even Igor is a stronger sprinter than he looks like he ought to be. He *can* run surprisingly fast ... it's just that "surprisingly fast" is a lower absolute bar to cross when you look like a scaly corgi.