Redefinition of the identity and phylogenetic position of Tityus trivittatus Kraepelin 1898, and description of Tityus carrilloi n. sp. (Scorpiones; Buthidae), the most medically important scorpion of southern South America.

: Tityus trivittatus is considered the most medically important scorpion species of southern South America. In this contribution we redefine its taxonomy, redescribe the species and separate the southern populations as a new species, Tityus carrilloi n. sp. As a consequence of this description, the most medically important species of the region turns out to be the new species herein described. We also clearly establish the phylogenetic position of both species through a dated molecular phylogenetic analysis based on four genes. Finally, we discuss the differences of the venom between the two species, and the epidemiologic implications of our results on the scorpionism problem in the region.