Three types of horned lizard can be found in Texas: the Texas horned lizard (Phrynosoma cornutum), the mountain short-horned lizard (P. douglasii hernandesi), and the round-tail horned lizard (P. modestum). The Texas horned lizard is the most widely known and the most prevalent in the state, and in 1993 was officially designated the state reptile by the Texas legislature. The Texas horned lizard, commonly called the "horny toad," is typically 2½ to 4 inches long and has a short, pointed snout, a broad, flat body, and a short tail. It has a prominent crown of spines at the back of its head, with two enlarged spines in the center giving the appearance of horns. There are rows of enlarged spines on either side of the throat. The Texas horned lizard also has two rows of spiny scales on each side of its body, which distinguishes it from the mountain short-horned lizard (which has only one row) and the round-tail horned lizard (no rows). The horned lizard's color varies from light brown to tan or grey to help it blend in with its habitat. Distinctive markings include dark brown spots with rims of yellow or white just behind the head. The horned lizard has several other defense mechanisms in addition to camouflage. It can puff up to twice its normal size, and its spines make it difficult for a predator to swallow. In addition, from ducts in its eyes it can squirt blood for a distance of several feet. The three horned lizard species found in Texas have a range that extends from central Kansas to the south and west through Oklahoma, Texas, and eastern Colorado and New Mexico. The Texas horned lizard can be found everywhere in Texas except for the piney woods region in East Texas. The horned lizard's diet consists principally of the harvester ant of the genus Pogonomyrmex. It also feeds on grasshoppers, isopods, small beetles, and beetle larvae.
The invasion of Texas by the red imported fire ant (Solenopsis invicta) and the consequent extensive use of insecticides in an attempt to control them, has at the same time reduced the population of harvester ants, greatly diminishing the food supply for the horned lizard. Field surveys conducted in 1992 by the Texas Parks and Wildlife Department indicated reduced populations of horned lizards in those areas where there is extensive agriculture and where the use of chemicals continues. Populations of Texas horned lizards are expected to remain stable in South and far West Texas unless major changes are made in how the land is used. The Texas horned lizard was one of the first animals to be listed as a threatened species in Texas (1977). The mountain short-horned lizard is also protected, but the round-tail, which is rarely seen in Texas, is not. Originally, protection for the Texas horned lizard was sought because it was being overcollected for the pet and curio trades. By the 1980s protective legislation had reduced the problem of overcollection, though the species remained threatened by the ongoing destruction of its habitat by agriculture and urban development. The most famous horned lizard in Texas was Old Rip, who supposedly spent some thirty years in the cornerstone of the courthouse in Eastland County. When freed, he became a celebrity, visiting President Calvin Coolidge in the White House in 1928. The increase in the capture and use of horned lizards as pets is often attributed to the fame attained by Old Rip. In the early 1990s the Horned Lizard Conservation Society was founded in Austin to help promote the preservation of the horned lizard.