Geographic range: Nearctic, Neotropical: P. orbiculare is endemic to Mexico, where it can be found on a fairly large area from Chihuahua in the north south to Puebla and Veracruz. (Chihuahua, Coahuila, Nuevo Leon, Durango, Zacatecas, San Luis Potosi, Jalisco, Aguascalientes, Guanajuato, Queretaro, Hidalgo, Michoacan, Mexico, Morelos, Tlaxcala, Puebla, Veracruz).

Physical characteristics: Middle -sized, dorsoventrally compressed lizard (8 -9 cm snout to vent, + 4,5 cm tail) of unmistakable appearance. Body stocky, displaying series of strongly keeled horn -like scales. The characteristic and species determining feature (as in all horned lizards) is the head, which in this species is flat, as long as wide, with two short but strong occipital horns and temporal horns extending almost as far as occipital horns. One row of abdominal fringe scales is present on the body flanks. Ventral scales are smooth. Tail short. Dorsal surface, tail, femoral and tibial regions are covered with granular scales among which various keeled scales are dispersed.
Color can be very variable, but usually dark brown with patterns of darker spots and stripes. Ventral surface is creamy colored.

Food habits: Feeds almost exclusively on ants (Formicidae), although other kinds of insects are also consumed.

Reproduction: Reproduction of this species is little known. The highest reproductive activity in males was recorded from May to June and females with embrya in middle July. This species belongs to the viviparous group inside the Phrynosomatidae, which includes species inhabiting drier and colder areas. Viviparity thus seems to be evolutionary adaptation to such environmental conditions.

Behavior: Horned lizards are solitary, diurnal animals. various antipredetor mechanisms have evolved: cryptical behavior is enhanced by body color matching the substarte, decreasing shadows due to spines and fringes of scales. When approached, remain motionless. Body armor also posess a serious riskif animal should be eaten.
At least four species of horned lizards (but not all species), coronatum, cornutum, orbiculare and solare, squirt blood from their eyes when attacked, especially by canine predators such as foxes and coyotes. The canine will drop a horned lizard after being squirted and attempt to wipe or shake the blood out of its mouth, clearly suggesting the fluid has a foul taste.

Habitat: Usually inhabits open forested areas (pine -oak) in vicinity of bunch grass, sand and rock formations.

Biomes: temperate forest

Conservation: Populations of horned lizards are declining throughout their entire area of distribution. The most important factor is habitat loss and alteration, but also collecting for trade has considerably decimated many species.

Phrynosoma orbiculare is listed as Endangered by the Mexican government in NOM-ECOL-059-2000