Two new species of Tyrannochthonius Chamberlin, 1929 (Pseudoscorpiones: Chthoniidae) from caves in Brazilian semiarid region.

Two new species of pseudoscorpions belonging to the genus Tyrannochthonius Chamberlin, 1929 are described from the semi-arid region of Brazil. Comprehensive morphological descriptions, diagnostic characters, and detailed illustrations are provided for Tyrannochthonius iuiu sp. nov. and Tyrannochthonius aratu sp. nov. Furthermore, we examine the remarkable diversity within Tyrannochthonius, emphasizing its widespread distribution in caves globally and documenting, for the first time, the association of species from this genus with subterranean habitats in Brazil. These findings highlight the significance of conserving such environments to safeguard their specialized fauna. Additionally, we characterize the habitats of the newly described species and present an identification key to the Tyrannochthonius species currently known from Brazil.