Bringing order to a complex system: phenotypic and genotypic evidence contribute to the taxonomy of (Scorpiones, Buthidae) and support the description of a new species.

We present a molecular phylogenetic analysis including a survey for overlooked phenotypic characters. Based on both analysis and characters a new cave-dwelling species is described: Tityus (Tityus) spelaeus from the Russão II cave, Posse, state of Goiás, Central Brazil. Characters such as the glandular regions of the female pectinal basal piece and basal middle lamellae of pectines, and the distribution of the ventral setae of telotarsi I-IV proved to be useful to constructing the taxonomy of species and species groups of . The new species is a member of the species-group of Tityus (Tityus) and can be readily recognized by the immaculate coloration pattern and the more developed glandular region on the female pectinal basal piece. In addition, we provide a discussion of the phylogenetic relationships observed within , on the relevance of the new phenotypic characters to the modern taxonomy of the genus , and to the records of Brazilian cave scorpions.