A new species of freshwater crab (Decapoda, Brachyura, Pseudothelphusidae) from the eastern Guiana Shield, and a note on Microthelphusa wymani (Rathbun, 1905)

Biological surveys conducted in the Tumucumaque Mountains, in the eastern portion of the Guiana Region, one on the Brazilian side, and the other on the French Guiana side, obtained specimens of pseudotelphusid freshwater crabs that belong to a new species of the family, Okothelphusa touroulti n. sp., which is described and illustrated here. The new species is the easternmost representative of the recently described genus, Okothelphusa Tavares & Magalhães, 2026, to which it is assigned due to a suite characters of its male first gonopod such as: marginal process straight and lamelliform; mesial process subtriangular to subrectangular and situated perpendicularly to main axis of the stem; apical plate subtriangular with similarly sized sternal and pleonal lamellae; and field of apical spines narrow and situated longitudinally on latero-pleonal side of apical plate. A comparison with the other three species of the genus is made based on their gonadal morphology and aspects of their geographic distribution are discussed. Taxonomic remarks on Microthelphusa wymani (Rathbun, 1905) are also presented, including a morphological description and detailed illustrations of the male first and second gonopods, including those of its type specimens.