The horned lizard has been affectionately called a "horny toad", or "horned frog" by generations of school children, who in the Southwest USA are taught that horny toads are actually lizards, not moist-skinned toads or frogs. The common names come from the lizard's flattened, rounded body and blunt snout, which make it resemble a toad or frog (Phrynosoma means "toad-bodied"), as well as its tendency, in common with larger true frogs and toads, to move sluggishly, making them easy to hand catch (such slow, undramatic movements may also avoid triggering attacks by predators, discussed later in this article). The spines on its back and sides are made from modified Reptile scales, whereas the horns on the heads are true horns (i.e. they have a bony core). Of 15 species of horned lizards in North America, eight are native to the United States. The largest-bodied and most widely distributed of the US species is the Texas horned lizard.