Chuckwallas are fairly large lizards and I am quite used to seeing them along our trails. Working in South Mountain Park for many years I am used to the dark black ones with bright orange tails. Over at Camelback, they are much greyer and the tails are hardly orange at all.
Anyhow, this little guy was under a rock at Papago, and you can probably tell from my fingers in the picture that I was the one turning over the rock. When it grows, it's tail will probably be bigger than the baby is right now.