Chuckwalla pictures (Sauromalus obesus).
Humans building homes in their desert lands have made life more difficult for the Chuckwalla. Now, it's so rare that the government considers it a "special concern" species.
The chuckwalla is very shy, and hides in rock crevices. If it's very scared, it inflates itself to wedge itself into the rock. They can grow to be 18 inches long, making it the second largest lizard in the US--second only to the 24-inch gila monster.