Abstract
In this contribution, we describe two new species of the burrowing crayfish genus Parastacus Huxley, 1879 from swamp forest fragments in the municipalities of Igrejinha and Bom Princípio, both in the Guaíba hydrographic region of the state of Rio Grande do Sul, southern Brazil. We provided a detailed morphological description and evaluated their conservation status according to the IUCN Red List Criteria. Parastacus paulae sp. nov. is distinguishable from the burrowing species of Rio Grande do Sul state in having a short triangular rostrum, prominent postorbital carinae, cervical groove strongly V-shaped, short pleon and subtrectangular telson with very small lateral spines. Parastacus mingusi sp. nov. is distinguishable from the burrowing species of Rio Grande do Sul state in having a short triangular rostrum with a concave dorsal surface, prominent postorbital carinae, globose chelipeds, short pleon and areola narrow. The extent of occurrence of P. paulae sp. nov. and P. mingusi sp. nov. were estimated at 576 km(2) and 662 km(2), respectively. The main threats identified were continued decline in the habitat quality, resulting from deforestation, habitat fragmentation, agriculture, urbanization and pollution. We suggest that both be categorized as Endangered.