The spider genus Nops MacLeay is revised, with redescriptions of 22 previously known species and descriptions of 12 new species. A new diagnosis for the genus is provided and keys to separate the species are proposed. After this revision Nops includes 34 extant species, thereof 15 (44%) occur in the Caribbean Islands, four (12%) in Central America and 15 (44%) in South America. Females of Nops meridionalis Keyserling and Nops gertschi Chickering are found and described for the first time. Three new synonymies are proposed: Nops virginicus Sánchez-Ruiz with Nops blandus Bryant, Nops craneae Chickering with Nops maculatus Simon and Nops proseni Birabén with Nops farhati Prosen. Four species are considered inquerenda: Nops anisitsi Strand, Nops bellulus Chamberlin, Nops branicki (Taczanowski) and Nops glaucus Hasselt. The following new species are described: N. jaragua n. sp., N. navassa n. sp., and N. pallidus n. sp. from the Caribbean region; N. campeche n. sp. and N. tico n. sp. from Central America, and N. alexenriquei n. sp., N. amazonas n. sp., N. bahia n. sp., N. ipojuca n. sp., N. itapetinga n. sp., N. minas n. sp. and N. pocone n. sp. from South America. New geographical records and distribution maps are provided for all species, with illustrations and reviewed diagnoses. The Nops species are restricted to the Neotropical region, from the Caribbean Islands and Mexico to the north of Argentina. The highest species richness is concentrated in the Wider Caribbean Region, including Central America and the north of Colombia and Venezuela where 64.7% of the species occur. Endemism in the Caribbean islands is very high; most of these species are single island endemics. A cladistic analysis, based on morphological data, was executed to test the monophyly of the genus. This is the first cladistic analysis of Caponiidae, and it includes besides the Nops species, 1) the six other species that were transferred from Nops, now in the genera Orthonops, Cubanops, Tarsonops and Medionops, and 2) Nopsides ceralbonus Chamberlin and Nyetnops guarani Platnick Lise. Therefore, representatives of all known Nopinae genera are included in the ingroup. The data matrix comprises 41 taxa scored for 47 morphological characters. The analyses under equal weights resulted in six equally parsimonious trees of 99 steps. All these trees are congruent with a unique hypothesis for Nopinae genera. Thus, all topological differences among the most parsimonious trees were the consequence of different hypotheses of relationships within Nops. The same result was also found under implied weighting with constants of concavity k = 2 to 13, where the topology of all trees was congruent for a single Nopinae genera hypothesis, but relationships within Nops were not resolved. All analysis under equal and implied weights recovered the monophyly of Nops with high support values, but internal clades within the genus showed low branch supports. Our results thus suggest that to resolve the internal relationships of Nops, studies based on molecular evidence are necessary to counteract the deficit of morphological data. The hypothesis obtained for Nopinae showed high branch support values for most of clades, corroborating all the transfers made from Nops. Medionops was recovered as the sister group of Nops with high support values. Nops, Medionops and Nopsides form a closely related, distinct spider group among nopine, supported by five unambiguous synapomorphies. Two of these synapomorphies could be functionally related: the presence of an arolium on the anterior pretarsi and the elongated and dorsally reflexed unpaired claw on the anterior legs. Nopsides appears to be a genus with apomorphic characters, presenting highly modified legs, but lacking the crista and gladius, and gaining a pair of anterior lateral eyes. Nyetnops is sister to all other nopine genera. Our results identified the necessity of further studies on nopine leg structures (arolium, crista, gladius and adesmatic joints) to improve understanding of the phylogenetic relationships of Nopinae genera.
