Accepted by M. Arnedo: 27 Apr. 2017; published: 11 Jul. 2017 ZOOTAXA ISSN 1175-5326 (print edition) ISSN 1175-5334 (online edition) Copyright © 2017 Magnolia Press Zootaxa 4291 (1): 117–143 http://www.mapress.com/j/zt/ Article 117 https://doi.org/10.11646/zootaxa.4291.1.7 http://zoobank.org/urn:lsid:zoobank.org:pub:07981903-5F66-454D-8CF1-6E1077DB5333 A new genus with seven species of the Subfamily Nopinae (Araneae, Caponiidae) from the Neotropical region ALEXANDER SÁNCHEZ-RUIZ & ANTONIO D. BRESCOVIT Laboratório Especial de Coleções Zoológicas, Instituto Butantan, Av. Vital Brasil, 1500, Butantã, São Paulo 05503-900, SP, Brasil. E-mail: alex.sanchezruiz@hotmail.com Abstract The new genus Medionops is proposed for a group of caponiid spiders found in South America and Panama. Nops simla Chickering and Nops cesari Dupérré are transferred to this new genus. Additionally, five new species are described: the type species Medionops blades n. sp. from Colombia; Medionops claudiae n. sp., Medionops murici n. sp. and Medionops ramirezi n. sp. from Brazil; and Medionops tabay n. sp. from Venezuela. All of these species belong to the subfamily Nopinae and have the three membranous translucent modifications found in some other nopine genera. However, in this new genus, the ventral translucent keel on the anterior metatarsi (crista herein) is very short, almost unnoticeable or even absent in some species. The translucent extension of the membrane between the anterior metatarsi and tarsi (gladius here- in) retains the same shape, but it is absent in M. murici n. sp. Also, Medionops n. gen. species have an unpaired claw on all tarsi, which is elongate and dorsally reflexed, and is associated with a membranous globose translucent lobe (arolium herein); a structure present only in Nops MacLeay and Nopsides Chamberlin. Beside the characteristics mentioned above, members of this new genus differ from other nopine in the shape of labium and endites and in the conformation of male and female genitalia. The three membranous translucent modifications on legs of some nopine genera are discussed and their terminologies are standardized. Key words: taxonomy, arolium, haplogynae, new species, new genus, South America Introduction Over the last two years we have been working on a taxonomic revision of the genus Nops MacLeay, and we had access to an extensive amount of material from several collections and museums worldwide. This genus currently includes 31 extant species (World Spider Catalog, 2016) and one fossil (Dunlop et al., 2016); thus presenting the highest diversity in the family. Species of Nops can be separated from species of other nopine genera by a combination of characteristics (Sánchez-Ruiz et al., 2015), but currently these are the only two–eyed nopine exhibiting unpaired tarsal claws which are elongate and dorsally reflexed, at least on the anterior legs (Sánchez- Ruiz, 2004: fig. 5). Two species in this genus caught our attention, Nops simla Chickering and Nops cesari Dupérré. Both species present several differences in the conformation of male and female genitalia, the shape of labium and endites, and some modifications in the pretarsal morphology, as compared with all other Nops species. Nops simla was described from Arima Valley in Trinidad Island, but also was recorded by Nentwig (1993) from the Canal Zone in Panama, where Nops largus Chickering is particularly abundant (Chickering, 1967). However, Nentwig´s (1993: figs 49a–c) illustrations of the male palp, abdomen and carapace, leave no doubt about the identity of specimens of Nops simla from Panama. Considering the restricted distribution of most Nops species (World Spider Catalog, 2016), Nops simla seems to be quite unusual with its larger distributional range. The male palp of this species has a long embolus that protrudes dorsally from the proximal–posterior prolateral surface of the bulb, making a strong curvature near its base toward the ventral part of the animal (see Chickering, 1967: fig. 16; Nentwig, 1993: fig. 49a). We noted that this conformation of the male palpal morphology of Nops simla is also present in Nops cesari (see Dupérré, 2014: figs 2–3), and it is very different from the conformation of all other Nops species (see Sánchez-Ruiz et al., 2015: figs 77–80). We also noted that these two species have the same endite and labium shapes, which differ from those of all other Nops species, and even from species of other nopine genera.