It's a greater/mountain short-horned lizard, Phrynosoma hernandesi.    From Wordnik.com.  [Archive 2008-05-01] Reference

The Pygmy short horned lizard (Phrynosoma douglassii) is extirpated.    From Wordnik.com.  [Reptile] Reference

California's coast horned lizard, Phrynosoma coronatum, has been split into three species.    From Wordnik.com.  [New Horned Lizards] Reference

Short-horned lizard (Phrynosoma douglassi) and western rattlesnake (Crotalus viridis) occur here as well.    From Wordnik.com.  [Northern short grasslands] Reference

Four of the hotspot's nearly 70 reptiles are endemic, including two that are found only on Cedros Island, off the Baja California Peninsula: the Cedros Island diamond rattlesnake (Crotalus exsul) and Cedros Island horned lizard (Phrynosoma cerroense).    From Wordnik.com.  [Biological diversity in the California Floristic Province] Reference

Phrynosoma cornutum, and things clearly went horribly wrong.    From Wordnik.com.  [ScienceBlogs Channel : Life Science] Reference

In the sandy soil of this region I found a new strange animal, the so-called horn-frog (Phrynosoma cornuta).    From Wordnik.com.  [A JOURNEY TO THE ROCKY MOUNTAINS IN 1839] Reference

In the study, published this week in the early online edition of the journal Proceedings of the National Academy of Sciences, researchers found that when the coast horned lizard (Phrynosoma coronatum) moved north from Baja California and spread throughout the state, it diverged into at least two new species.    From Wordnik.com.  [AOL News] Reference

Several lizards are centered in the Chihuahuan Desert, and include the Texas horned lizard (Phrynosoma cornutum), Texas banded gecko (Coleonyx brevis), reticulated gecko (C. reticulatus), greater earless lizard (Cophosaurus texanus), several species of spiny lizards (Scelpoprus spp.), and marbled whiptails (Cnemidophorus tigris marmoratus).    From Wordnik.com.  [Chihuahuan desert] Reference

Other wildlife characteristic of the moist mixed grassland are black-tailed and white-tailed deer (Odocoileus hemionus and O. virginianus), pronghorn antelope (Antilocapra americana), coyote (Canis latrans), short-horned lizard (Phrynosoma douglassi), western rattlesnake (Crotalus viridis), rabbit (Sylvilagus sp.) and sage grouse (Centrocercus urophasianus).    From Wordnik.com.  [Northern mixed grasslands] Reference

These Canadian reptiles are listed as vulnerable: spotted turtle (Clemmys guttata) wood turtle (Clemmys insculpta) northern prairie skink (Eumeces septentrionalis) eastern yellow-bellied racer (Coluber constrictor flaviventris) eastern short-horned lizard (Phrynosoma douglassi brevirostre) eastern hognose snake (Heterodon platirhinos) (Source: Biodiversity Institute of Ontario).    From Wordnik.com.  [Reptile] Reference

Lizards are numerous, including Bailey's collared lizard (Crotaphytus collaris baileyi), western earless lizard (Holbrookia maculata approximans), southern brownshouldered uta (Uta stansburiana elegans), striped swift (Sceloporus consobrinus), and horned toads (Phrynosoma sp.).    From Wordnik.com.  [Tseh So, a Small House Ruin, Chaco Canyon, New Mexico :] Reference

‘Death by piercing’ isn’t limited to big snakes – Klauber (1982) reported that horned toads Phrynosoma may kill snakes that try to swallow them (the lizard’s horns perforate the snake’s throat) and Ramírez-Bautista and Uribe (1992) described the case of a Lyre snake Trimorphodon biscutatus (a terrestrial colubrid) that died after the spiny tail scales of a Spiny-tailed iguana Ctenosaura pectinata pierced the snake’s stomach and oesophagus.    From Wordnik.com.  [Archive 2006-02-01] Reference

However, the following avifauna and herpetofauna are characteristic of the Mojave region in particular: LeConte’s thrasher (Toxostoma lecontei), banded gecko (Coleonyx variegatus), desert iguana (Dipsosaurus dorsalis), chuckwalla (Sauromalus obesus), and regal horned lizard (Phrynosoma solare).    From Wordnik.com.  [Mojave desert] Reference

Phrynosoma douglasii.).    From Wordnik.com.  [grouse Diary Entry] Reference

A large number of specialist and endemic species of plants and animals are found here, including the Quino checkerspot butterfly (Euphydryas editha quino), Hermes copper butterfly (Lycaena hermes), San Diego thorn mint (Acanthomintha ilicifolia), San Diego ambrosia (Ambrosia pumila), San Diego barrel cactus (Ferocactus viridescens), San Diego pocket mouse (Perognathus fallax), Merriam kangaroo rat (Dipodomys merriami), Stephens kangaroo rat (Dipodomys stephensi), red-diamond rattlesnake (Crotalus ruber), San Diego banded gecko (Coleonyx variegatus abbotti), San Diego horned lizard (Phrynosoma coronatum blainvillei), California gnatcatcher (Polioptila californica), and the coastal populations of the cactus wren (Campylorhyncus brunneicapillus).    From Wordnik.com.  [California coastal sage and chaparral] Reference