Figure 1

Localities sampled for the Tropidurus semitaeniatus species group and outgroups. Limits of the Caatinga are outlined in black and the current São Francisco River configuration in blue. Numbers correspond to locality names in Table 1 and colored symbols follow the same colors for clades in Figure 2. The white star right by locality number 50 is the type locality for T. semitaeniatus (Sincorá Velho, BA). The major geomorphological features discussed in the text are highlighted (AraPl = Araripe Plateau; CCHigh = Central Ceará Highlands/Serra da Ibiapaba, JaVa = Jaguaribe river valley, BoPl = Borborema Plateau). Major paleocourse phases of the SFR correspond to: (a) early opening to the equatorial Atlantic Ocean; (b) paleolacustrine phase; (c) forsaken meanders located to the south of the present mouth; and (d) the current course.