The giant horned lizard (''Phrynosoma asio'') is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of phrynosomatid

lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...

which is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the Pacific coast of southern

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

. It is the largest horned lizard and is also the most slender (it has a more typical lizard-like appearance). It is able to survive in the desert. The spines on its back and sides are made from modified scales, whereas the horns on its head are true horns (i.e., they have a bony core). They are commonly named for their large size, which can reach up to 6 to 8 inches from snout to tail, hence the name.

References

{{Taxonbar, from=Q3010278 Phrynosoma Fauna of Southern Mexico Reptiles of Mexico Reptiles described in 1864 Taxa named by Edward Drinker Cope