Figure 4. "Standard" karyotypes of the four crevice-using species groups. Karyotypes are arranged in columnar fashion to facilitate interspecific comparisons; A. Sceloporus mucronatus ♂ (Mexico: Veracruz; 4 km ESE Las Vigas); B. "S" or standard S. grammicus ♂ (Mexico: Coahuila; 13 km SSE Arteaga on Mex. Hwy. 57); C. S. shannorum ♂ (Mexico: Sinaloa; 14 km ENE Copala, 1950 m elev.); D. S. heterolepis ♀ (Mexico: Jalisco; 2400 m elev. on Cerro Tequila, 10 km S Tequila). E. S. megalepidurus megalepidurus X S. m. pictus intergrade ♂ (Mexico: Puebia; 8 km SE Ciudad Serdan); F. S. megalepidurus megalepidurus ♂ (Mexico: Puebia; 5 km NW Atenco); and G. S. asper ♂ (Mexico: Mayarit; 35 km SE Tepic, 1200 m elev.). The scale A bar in column D between pairs 5 and 6 represents 10 µm. The similarity of the "Em" chromosomes, indicated by the box crossing columns E, F, and G, may be seen more clearly by comparing the Em and Y chromosomes within each karyotype to control for differences in fixation and staining among the species.