Figure 1. Radiation of the small-scaled Sceloporus. Names of the species groups are in capital letters. Species for which karyotypic information exists are underlined. Sources of this information are cited in Table 1. Karyotypically derived species or species groups are boxed by solid borders. The phylogenetic interpretation is mine, and will be justified elsewhere; however it is largely consistent with Smith (1939), Larsen and Tanner (1974, 1975), and Thomas and Dixon (1976), as controlled by biogeographic considerations. Sceloporus couchi shares more characters of its squamation with other sceloporine genera than do any of the small-scaled species (Hall, in prep.), and remains relatively unspecialized. The jalapae group species are derived with respect to couchi, but remain relatively unspecialized with respect to other Sceloporus. The sequence of chromosomal derivation (A), leading to S. merriami involves the fixation of 6 macrochromosomal centric fissions. The karyotypic information for S. maculosus is all somewhat dubious (see Table 1 and text), but it is possible that the 2n±40 maculosus might represent a surviving intermediate in this sequence, although this would present biogeographic problems. The sequence of chromosomal derivation (B) leading to the scalaris group involves the fixation of 5 microchromosomal fusions.