This lizard was observed while volunteering by putting up trail markers at Inks Lake State Park outside of Burnet. At the time, I had no idea what kind of lizard it was. With the help of the internet and the iNaturalist community, it was identified as an Eastern Collared Lizard.
Like other collared lizards, the Eastern Collared Lizard (Crotaphytus collaris) is known for its high speed running on its hind legs. It also is diurnal, basking in the sunlight during daylight hours. These lizards are highly territorial, and in captivity, males will fight to the death if placed together. They are found primarily in the dry, open regions of Mexico and south-central United States.
My iNaturalist post can be found here.
Sources: http://www.reptilesofaz.org/Lizards-Subpages/h-c-collaris.html; http://www.inaturalist.org/taxa/33135-Crotaphytus-collaris