Young Chuckwalla (Sauromalus ater) spotted in Death Valley.
Chuckwalla belong to the Iguana family, and they look like fat, chubby lizards. But they are excellent climbers, and this one was able to climb a vertical wall of marble rock that was rather smooth.
For more information about Chuckwallas, read digital-desert.com/wildlife/lizards/chuckwalla.html and en.wikipedia.org/wiki/Sauromalus_ater.