Two new species of Chaco Tullgren from the Atlantic coast of Uruguay (Araneae, Mygalomorphae, Nemesiidae)

Abstract. We describe two new species of the nemesiid spider genus Chaco from Rocha Province, Uruguay. These new species are diagnosed based on genital morphology, male tibial apophysis spination, and burrow entrance. We test cospecificity of one species, Chaco costai,via laboratory mating experiments. The new species are diagnosed and illustrated and habitat characteristics, and capture behavior are described. We conduct a cladistic analysis based on a previously published morphological character matrix that now includes the newly described species.