This lizard is most likely in the genus Sceloporus because of the “keel” visible in the center of its larger scales. It closely resembles the species S. undulata, the Prairie lizard due to its light stripe dark stripe, and light stripe visible along its sides. Also, the brown stripe down the middle of the back is expected in S. undulata. Several subspecies of S. undulata have been identified which further complicates identification of the animal pictured above.
Over the last 40 years, there have been some genetic comparisons done that may have changed the taxonomic status of S. undulata and its subspecies’. Take a look here and you should glean from this source that S. undulata consobrinus may have been elevated from a subspecies to species and renamed Sceloporus consobrinus. Since I did not get to examine this specimen more closely, I refrained from using the old subspecies name or its new name. Although, the animal in the picture above is most likely, based on the markings visible, to be Sceloporus undulatus consobrinus, the Southern Prairie Lizard. Also, I have an old field guide that says this species should occur in Tarrant County, Texas where the photo was taken.
Without the organism in hand, this identification is and will remain tentative. Also, the variety of markings I have seen across the internet sites on reptiles, plus the number of subspecies for S. undulata identified at the link above means there is a fair amount of variation in markings across this species. Random variation within a species worked on by environmental constraints is the machinery of evolution.
Nonetheless, I enjoyed the few moments I had with this little fella. He allowed me to follow along as he scampered along a wooden handrail in a wooded area adjacent to a marshland. I watched him scamper up a tree and disappear into the foliage. Most of the lizards I see regularly in the parts of Texas where I have lived have been Sceloporus. We used to have one that liked to come down our chimney into the house and scare the crap out of folks when he darted through the house. I kept a monofilament noose on a 36 inch piece of 3/8th inch dowel handy to help catch the little guy when he strayed into the house. We saw him grow and get fat over several years.