Figure 3. Derivation of the 2n=22 species of Sceloporus. Lettering style follows Fig. 1. Phylogenetic interpretations are mine, and will be justified in detail elsewhere. However, it is worth note that Smith (1939) treats zosteromus as a subspecies of magister, and that among the 2n=22 egg layers, spinosus, olivaceus, and horridus all closely resemble magister. I have collected probable intergrades between cautus (Smith's [1939] undulatus group) and olivaceus (Smith's spinosus group) in valleys to the south and east of Monterrey, Nuevo Leon, which offer potential paths for gene flow between cautus on the Plateau and olivaceus on the coastal plane. Larsen and Tanner (1974, 1974) also note a close similarity between these two species. The formosus group probably derives from southern representatives of the horridus group which crossed the Isthmus of Tehuantepec and became adapted to high elevations. The subgroup salvini-formosus represent a radiation of formosus group species which crossed the Isthmus back into the central highlands of Mexico.