“…The region is bordered to the east by what is probably the most wellknown biogeographic boundary recognised today, Wallace's Line. A second but lesser-known biogeographic boundary occurs at the transition zone between the Sundaic and Indochinese biotas (sensu Woodruff, 2003) in the vicinity of the Isthmus of Kra (Figure 1), with distinct assemblages of amphibians (Inger, 1966; see review by Inger and Voris, 2001), reptiles (Inger and Voris, 2001), birds (Hughes et al, 2003), mammals (Corbett and Hill, 1992), insects (Corbet, 1941) and plants (Ridder-Numan, 1998;Denduangboripant and Cronk, 2000) limited to varying degrees either side of this barrier. Recently, it has been hypothesised that marine transgressions may have produced this pattern (Woodruff, 2003); specifically, that and Pliocene-era (5.5-4.5 Mya) high sea-level stands resulted in two seaways that dissected the Thai-Malay Peninsula (Figure 1; Woodruff, 2003), for durations in excess of 1 million years.…”