Its the Giant Texas Blue Spiny! I have 6 3-4 month old babies here, and was researching when they become sexually mature because mine are already starting to look like monsters. So I found this:

Blue Spiny Lizards are the largest of all native Spiny lizards.

Here is the source. You'll have to scroll down, and there is a pic of a woman holding a MONSTER blue spiny!
tp://www.sbs.utexas.edu/halldw/Bio455L/Files/STexasFall042.html

They are gonna eat me out of house and home!