Phylogenetic relationships of a new species of pseudoxyrhophiine snake (Reptilia: Lamprophiidae: Thamnosophis) suggest a biogeographical link between western and northern Madagascar

We describe a new species of the pseudoxyrhophiine snake genus Thamnosophis from a dry forest of the karstic massif Tsingy de Bemaraha in central western Madagascar. Thamnosophis mavotenda sp. n. is characterised by 19 dorsal scale rows, 188 ventrals, 110 subcaudals, and by colouration (e.g. yellow head sides). Morphological and molecular phylogenetic data indicate that the species is most closely related to the recently described Thamnosophis martae from the far north of the island which inhabits dry karstic forest and subhumid lowland rainforest. This species pair represents a well-supported example of a sister-group relationship in snakes between northern Madagascar and the Tsingy de Bemaraha plateau, and corroborates preliminary observations in other reptile species. We discuss this finding in the light of recent hypotheses on the biogeographic zonation of Madagascar.