Addressing knowledge gaps in Brazilian cave fauna: description of a new genus and new species of Pseudoscorpions (Arachnida: Pseudoscorpiones)

Abstract

The Brazilian subterranean biodiversity remains significantly underexplored, a condition that exacerbates the Linnean and Racovitzian shortfalls – the gaps between known species and their actual existence and distribution in nature. This taxonomic impediment is particularly critical for the order Pseudoscorpiones, where the lack of formal descriptions hinders the legal protection of cave environments increasingly threatened by mining and deforestation. This dissertation addresses these gaps by providing a systematic reassessment of the family Chthoniidae in Brazil, integrating historical data with the description of new taxa from the Amazon, Caatinga, and Atlantic Forest biomes. In the first chapter, the long-standing taxonomic inconsistency regarding the "unusual" species Pseudochthonius orthodactylus Muchmore, 1970, is resolved. Based on a detailed morphological analysis of type material and new specimens, the genus Kayapochthonius gen. nov. is established. This new genus is distinguished by robust, straight chelae and a highly developed chelal apodeme, traits that bridge the morphological gap between Pseudochthonius and Aphrastochthonius. Within this framework, P. orthodactylus is reallocated as Kayapochthonius orthodactylus comb. nov., and two new species are described: Kayapochthonius bacaba sp. nov., from the ferruginous landscapes of Carajás (PA), and Kayapochthonius diamantinus sp. nov., from a cave in Chapada Diamantina (BA). The second chapter focuses on the diversity of the genus Pseudochthoniusin northeastern Brazil, describing three new species from limestone caves in Ceará state: Pseudochthonius ubajara sp. nov., P. andyratinga sp. nov., and P. tejussuocasp. nov.. Morphological features, such as elongated appendages and reduced ocular structures, led to the classification of P. ubajara sp. nov. and P. andyratinga sp. nov. as troglobionts, while P. tejussuoca sp. nov. is considered a troglophile. Furthermore, this study reports the first documented case of syntopy within the genus Pseudochthonius, with P. ubajarasp. nov. and P. andyratinga sp. nov. co-occurring in Morcego Branco Cave. Collectively, these results demonstrate that the diversity of Brazilian cave-dwelling pseudoscorpions is significantly underestimated. By formalizing these descriptions and providing identification keys, this work contributes essential data for environmental impact assessments and the legal safeguarding of Brazil's speleological heritage, ensuring that these unique evolutionary lineages receive the protection required by current legislation.