Casque-headed Basilisk, Casque-headed Lizard, Old Man Lizard, Helmeted Iguana
These lizards rely on their camouflage to an almost ludicrous extent. They sit absolutely still, usually perched vertically as in the first picture above. They are among the most cooperative saurian photo models you could hope for, though I should admit that one of the two got tired of me taking its picture after about fifteen minutes and made a half-hearted dash for freedom, which was easily thwarted. We released both of these in some vegetation near the cabins at the lodge, and they remained in the same places for at least two days (then we left town).