On a warm spring morning a few years ago, I ducked into a rock shelter on Austin’s Barton Creek Greenbelt while taking a walk. Sunlight cut through the live oaks and painted the walls of the limestone canyons. Only as I stood up to leave did I see it: a slender, serpentine lizard sitting on a ledge, its armored back banded in orange and white, its narrow face and glittering eyes set in an expression of faint distaste.Wild lizards don’t like to be seen, but the Texas alligator lizard (Gerrhonotus infernalis) has elevated elusiveness to an art form. Arguably one of the most distinctive Texas reptiles, it’s found across the Hill Country, particularly in the heavily trafficked trails near Austin’s urban core. But it’s famously…