It has been proposed that the subgenus Archaeotityus comprises the most ancient species group within the medically important scorpion genus Tityus. cDNA encoding sodium-channel active toxins from the type species of this subgenus, Tityus clathratus (central Venezuela), have been isolated and sequenced. Two cDNAs were retrieved that encoded 61 amino acid-long putative neurotoxins named Tcl1 and Tcl2. Sequence identity was highest (87%) when both were compared with β-toxin Ts1 from the Brazilian scorpion Tityus serrulatus and its homologs from T. bahiensis, T. stigmurus, and T. costatus. A Bayesian analysis indicated statistical support for the grouping of T. clathratus Tcl1 and Tcl2 with Brazilian gamma-like β-toxins, reinforcing previous phylogenetic studies which suggested an evolutionary relationship between the subgenus Archaeotityus and scorpion species inhabiting southeast South America belonging to the subgenus Tityus.Consejo de Desarrollo Científico y Humanístico de la Universidad Central de Venezuela