Chuckwalla
They are big and they look mean, but Chuckwallas (Sauromalus ater) are harmless herbivores feeding on desert flowers, fruits and leaves. Young chuckwallas are known to try a grasshopper or two, but usually stick entirely to plants by the time they are a year old. Chuckwallas get all their water from the plants they eat and never drink, even when water is readily available. Instead of urination to void their body of salts, these wastes pass through and build in their nostrils as crust which breaks up and falls out when the reptile exhales. They are adept at living in rocky areas under 4,000 feet elevation. As well as dodging into cracks of the rocks in which they live when threatened, they inflate themselves with air making it nearly impossible to remove them by brute strength.
http://digital-desert.com/wildlife/chuckwalla.html
.