A new genus, Paradysderina, is established for a speciose group of Andean goblin spiders belonging to the Dysderina complex. Members of Paradysderina resemble those of Scaphidys derina Platnick and Dupérré in having the dorsal abdominal scutum of females either greatly reduced or entirely absent, but lack the highly crenulated sternum characteristic of Scaphidysderina and have instead a distinctively flattened, rugose sternal surface. Males of various species of Paradysderina show a wide range of remarkable autapomorphies, including projections at the sides of the clypeus and various kinds of excavations and projections on or between the chelicerae.
Several species share the highly unusual occurrence of asymmetry between the left and right male pedipalps; in some species the asymmetry involves the size of the palpal bulb, but in those and other cases, the embolus structure also differs consistently between the two sides, to such an extent that if the left and right palps were studied in isolation, they would be considered to belong to different species.
Dysderina globosa (Keyserling) from Colombia and D. montana (Keyserling) from Peru are transferred to Paradysderina, and their males are described for the first time.
A total of 52 new species are described, including 26 from Peru (P. watrousi, P. consuelo, P. excavata, P. silvae, P. malkini, P. maldonado, P. asymmetrica, P. apurimac, P. convencion, P. macho, P. tambopata, P. schizo, P. wygodzinskyi, P. newtoni, P. thayerae, P. carpish, P. rothae, P. tabaconas, P. sauce, P. piura, P. tambo, P. fatima, P. bagua, P. yasua, P. loreto, and P. pithecia), 15 from Ecuador (P. zamora, P. lostayos, P. puyo, P. hermani, P. yanayacu, P. baehrae, P. righty, P. centro, P. fusiscuta, P. lefty, P. vlad, P. yasuni, P. dracula, P. pecki, and P. sucumbios), and 11 from Colombia (P. imir, P. pinzoni, P. leticia, P. pira, P. vaupes, P. huila, P. chingaza, P. boyaca, P. carrizal, P. monstrosa, and P. chinacota); P. loreto is also recorded from far western Amazonas, Brazil.
A second new genus, Semidysderina, is established for species that share with Scaphidysderina and Paradysderina the absence of a dorsal scutum in females and a spinneret scutum in both sexes, but differ in having a groove connecting the posterior spiracles. Six new species of Semidysderina are described from Colombia (S. lagila, S. kochalkai, S. donachui, S. marta, S. mulleri, and S. sturmi). At least four of these species, from the Sierra Nevada de Santa Marta, are remarkable for the retention of a distinct seam between the male palpal cymbium and bulb.