During our hike near Ajalpan we saw many large grey colored lizards running away from us. At that time I had no idea of what species I was looking at, but Tim Burkhardt identified the above lizard as Aspidoscelis sacki. The lizard was first in the genus Cnemidophorus but has been moved to the genus Aspidoscelis (Reeder et al. 2002). The common names for this species: Sack's giant whiptail, Blue-bellied Racerunner.
In the above photo you can see several of the large light blue scales and black scales that cover the underbelly of the lizard. Since almost every lizard of this species we encountered that day ran away so fast that it looked like it was flying low above the ground, the common name Blue-bellied Racerunner is well-deserved.
For another photo of this beautiful specimen, see: Sack's giant whiptail lizard (Aspidoscelis sacki)
This photo is part of the blog entry Police encounters, which has habitat photos and describes the environment.