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In many species, sexual dimorphism increases with body size when males are the larger sex but decreases when females are the larger sex, a macro-evolutionary pattern known as Rensch's rule (RR). Although empirical studies usually focus exclusively on body size, Rensch's original proposal included sexual differences in other traits, such as ornaments and weapons. Here, we used a clade of harvestmen to investigate whether two traits follow RR: body size and length of the fourth pair of legs (legs IV), which are used as weapons in male-male fights. We found that males were slightly smaller than females and body size did not follow RR, whereas legs IV were much longer in males and followed RR. We propose that sexual selection might be stronger on legs IV length than on body size in males, and we discuss the potential role of condition dependence in the emergence of RR.

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Harvestmen (Arachnida: Opiliones) were among the earliest terrestrial arthropods but their unmineralized exoskeletons are scarce and often fragmentary as fossils (Palencia et al. 2019). Consequently, the discovery and interpretations of fossil harvestmen from the early Palaeozoic can have disproportionate effects on the understanding of evolution in Opiliones. Recently, Devonopilio hutchinsoni Tihelka, Tian Cai, 2020, was described as a new fossil harvestman from the well-known Rhynie chert deposits of Scotland, an important source of information on freshwater and terrestrial ecosystems of the early Devonian (Tihelka et al. 2020). This species would be one of the earliest records of harvestmen. The description was based on a single slide showing fragments of arthropod cuticle, which Tihelka et al. interpreted as a harvestmen penis and unspecified associated body parts. As specialists on harvestman morphology and systematics, we were intrigued by these conclusions. However, based on the material presented by Tihelka et al. we find no compelling evidence supporting the proposal that the specimen is a harvestman.

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The "World Catalogue of Opiliones" (WCO) is a collaborative effort to comprehensively index the Earth's species of harvestmen. This paper announces one component of the WCO, "WCO-Lite" a website available at https://wcolite.com/. WCO-Lite provides a graphic user interface for a second component of the WCO, "Opiliones of the World", a database on the taxonomy of the harvestmen curated in TaxonWorks (TW). WCO-Lite interfaces include: (1) a checklist of all valid taxa of the arachnid Opiliones, exhaustive up to December 2018; (2) a taxonomic tree; (3) a search engine comprising two modules; and (4) a counter of species diversity for each taxon. An e-Book companion was launched simultaneously with WCO-Lite version 1.1 on September 12, 2020 to account for the formal publication of mandatory nomenclatural changes and availability of taxonomic names. The collective components of the WCO are also being summarized in a forthcoming conventional paper-form catalogue, currently in manuscript stage.

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Promecostethus unifalculatus Enderlein, 1909, is the only representative of the order Opiliones from the Crozet Islands. The species belongs to the family Triaenonychidae and is biogeographically interesting because it is a candidate for transoceanic dispersal, a very rare event in this ancient family. Despite this significance, P. unifalculatus is taxonomically still poorly known, and a redescription of this species using modern taxonomic standards is urgently needed. Here we redescribe the species, offer the first description and illustrations of the male genitalia and provide a full exomorphological survey of the species using scanning electron microscopy. Furthermore, we provide an emended diagnosis for the genus Promecostethus and discuss its relationship with some morphologically similar genera.

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In this paper, we describe a new subfamily of Gonyleptidae, Paragoniosomatinae subfam. nov., based on a new genus and species, Paragoniosoma cachaceiro gen. nov., sp. nov., found in an upper montane cloud forest of Chapada Diamantina mountains, one of the small interior patches of Atlantic Forest. This discovery suggests that the narrow-restricted cloud forests are old relicts of an Atlantic Forest hotspot. Paragoniosoma cachaceiro gen. nov., sp. nov. is characterized by the presence of four areas on the dorsal scutum, serose dry mark in areas III-IV, seven basal setae in penis (macrosetae A and B) in two rows, and very large tarsal process. We performed a phylogenetic analysis based on morphological characters that revealed a close relationship of the new species with Goniosomatinae, a subfamily that includes six genera and 38 valid species distributed throughout the coastal Atlantic Forest. The new species also has the same habitat and other behavioural and ecological traits as Goniosomatinae, furnishing great insights on the evolution of their characteristic biology, e.g., subsocial behavior. Field surveys of harvestmen from the type locality and nearby lowland seasonal forests indicate a unique fauna, including additional new, undescribed species. In addition to phylogenetics, this dissimilarity with other regions and the presence of endemic species of other animal and plant taxa provide support for the consideration of the cloud montane patches of Chapada Diamantina as relicts. We discuss this rule in the historical biogeographic context of Atlantic Forest and suggest that the new species represents evidence of an Atlantic Forest that was more widespread in the past.

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Introducción: Los arácnidos de la isla del Coco representan 50 especies, ubicadas en seis órdenes y 26 familias. El trabajo de actualización del conocimiento de la fauna de este grupo de animales en la isla inició no sistemáticamente hace más de 127 años, donde un escorpión se convirtió en el primer espécimen citado del grupo. Objetivo: Actualizar la lista de especies de arácnidos para la Isla del Coco, aportando nueva información sobre taxones poco conocidos y describiendo nuevas especies. Métodos: Durante dos expediciones, llevadas a cabo del 11 al 22 de abril 2013 y del 8 al 18 julio 2017, se recolectaron arácnidos con métodos manuales y trampas, se preservaron en etanol y se realizaron las identificaciones en laboratorio. Los rangos de distribución están basados en el catálogo de arañas del mundo, las identificaciones realizadas, se respaldan en la literatura específica citada para cada caso y las sugerencias biogeográficas presentadas de los grupos o especies tratadas, surgen del análisis de los patrones de distribución general que presenta el género o grupo citado. Resultados: Los hallazgos principales incluyen la adición de nuevos registros de especies para la isla, un orden, 11 familias y 29 especies, de las cuales tres son nuevas para la ciencia. Conclusiones: Es necesario continuar con el inventario de la aracnofauna de la isla, principalmente en los sectores que no han podido ser previamente muestreados. A nivel biogeográfico la fauna de arañas que habita la isla está mayormente relacionadas con Centroamérica, mientras que las especies de hábitos cosmopolitas posiblemente sean de reciente introducción.

Introduction: The arachnids of Isla del Coco represent 50 species, located in six orders and 26 families. The work of updating the knowledge of the fauna of this group of animals on the island began not systematically more than 127 years ago, where a scorpion became the first specimen cited in the group. Objective: To update the list of arachnid species for Coco Island, providing new information about little-known taxa and describing new species. Methods: During two expeditions, carried out from April 11 to 22, 2013 and from July 8 to 18, 2017, arachnids were collected with manual methods and traps, preserved in ethanol and identified in the laboratory. The distribution ranges are based on the spiders catalog of the world, the identifications made, are supported by the specific literature cited for each case and the biogeographical suggestions presented of the groups or species treated, arise from the analysis of the general distribution patterns that presents the genus or group cited. Results: The main findings include the addition of new species records for the island, one order, 11 families and 29 species, of which three are new to science. Conclusions: It is necessary to continue with the inventory of the island fauna, mainly in the sectors that could not be previously sampled. At the biogeographical level, the spider fauna that inhabits the island is mostly related to Central America, while the species with cosmopolitan habits are possibly of recent introduction.

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A new species of the cosmetid harvestman genus Taito Kury Barros 2014 is described from the Área de Conservación Privada (ACP) Panguana, Peruvian Amazonia, which extends the distribution range of the genus to the south-west. The herein described species Taito adrik sp. nov. differs from all other known species of the genus by the distinct shape of the equuleus, the armature of leg IV in males, and the structure of male genitalia, in combination with features of the chelicerae and the anal operculum. In addition, COI barcodes of the new species are provided.

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Two new genera, Ampliphallus gen. nov. and Guelaguetzia gen. nov., are described from material collected in the state of Oaxaca, Mexico. The genus Ampliphallus gen. nov. is monotypic and contains the species A. chimalapaensis sp. nov., from the tropical rain forest of Santa María Chimalapa, Oaxaca. The genus Guelaguetzia gen. nov. is composed of two species: G. cuicateca sp. nov. (type species) and G. serrana sp. nov., from pine forests in northern Oaxaca. These genera can be recognized from each other mainly by the armature of leg IV and by the male genitalia; both are also compared with the remaining members of the Stygnopsinae. An identification key for all genera of the subfamily is provided.

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Two new Colombian species of Quindina Roewer, 1915 are here described based on genital morphology and external characters. Quindina hermesi sp. nov. (type locality: Bolívar, San Jacinto) can be diagnosed externally by having a combination of colored tubercles on the ocularium, the anterior margin, areas I, II and IV of the dorsal scutum, and the free tergites; Q. discolor sp. nov. (type locality: Magdalena, Ciénaga) shows a different combination of colored tubercles on the ocularium and lateral margins. Phylogenetic analyses were performed by adding both new species to an existing matrix for Nomoclastidae. The analyses resulted in various topologies for the relationships among Nomoclastes Sørensen, 1932, Napostygnus Roewer, 1929, Kichua Pinto-da-Rocha Bragagnolo, 2017, Callcosma Roewer, 1932 and Quindina Roewer, 1914, but all analyses recovered the monophyly of Callcosma and Quindina. This constitutes the first record of the family in northern Colombia.

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A new genus of Gonyleptidae Pachylinae, Qorimayus gen. nov., is described to place the high-altitude species originally named Parabalta alticola Ringuelet, endemic to Sierra de Famatina, western Argentina. While classical exomorphological features do not separate this new genus from Parabalta Roewer or Pachyloides Holmberg (to which the species was formerly combined), male genitalic features, especially the shape of the ventral process of stylus, differ clearly. In turn, penis morphology suggests the systematic relationship of Qorimayus gen. nov. with the Chilean genera Metabalta Roewer and Nanophareus Roewer. A cladistic analysis was performed to test the phylogenetic affinities of the new genus; 28 terminals were used, comprising selected species of Parabalta, Pachyloides, Metabalta and Nanophareus, as well as other Gonyleptidae to represent the 'subtropical' and the 'Chilean' opiliofaunistic elements; the most external outgroups included one cosmetid, one metasarcid and one nomoclastid. Results supported the recognition of Qorimayus as an independent genus, and its close relationship with the Chilean genera Metabalta and Nanophareus. A detailed redescription of Qorimayus alticola comb. nov., along with some habitat notes are given. The presumed zoogeographical links of this endemic species with the central Chilean opiliofauna are briefly discussed.

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Erythraeidae Robineau-Desvoidy has 60 genera worldwide, of which Leptus Latreille has around 260 species described, with 15 of these recorded from Brazil. Here, we describe Leptus (Leptus) flechtmanni sp. n. from a cave in the state of Pará. Additional material attributed to this species is reported from other caves and also parasitizing a harvestman. In addition, SEM images and new Brazilian host records (Diplopoda and Hemiptera) are presented for Leptus (Leptus) haitlingeri from the states of São Paulo and Rio de Janeiro.

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As part of an ongoing revision and cladistic analysis of the "K92 clade" (Gonyleptidae), the Brazilian genus Progonyleptoidellus Piza, 1940 is revised and two new species from São Paulo State are described: P. bocaina sp. nov. and P. picinguaba sp. nov. A cladistic analysis of the genus was performed using these two new species plus the three previously described species of the genus [P. fuscopictus (B. Soares, 1942); P. orguensis (Soares Soares, 1954); and P. striatus (Roewer, 1913)], and 25 more additional gonyleptoid outgroup species, most being representatives of the K92 clade. The data matrix is composed of 109 characters: three from the ocularium, 24 from the dorsal scutum, six from the free tergites, nine from the pedipalp, 41 from the legs and 26 from male genitalia. The genus Progonyleptoidellus was recovered as monophyletic only with the exclusion of P. orguensis and was supported on the basis of only one exclusive synapomorphy: presence of dry-marks on sulci of dorsal scutum. Based on the cladistic analysis, P. orguensis was reallocated in Deltaspidium Roewer, 1927, herein considered a senior synonym of Adhynastes Roewer, 1930, and two new combinations are proposed: Deltaspidium orguense (Soares Soares, 1954) and Deltaspidium tenue (Roewer, 1930). Diagnoses are given for Progonyleptoidellus, the previously described species, (P. fuscopictus and P. striatus) and the two new species.

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Manahunca bielawskii Silhavý, 1973, the type species of the genus Manahunca Silhavý, 1973, is redescribed based on abundant material from the type locality, including new data on its morphological variability and penis morphology. A neotype for M. bielawskii is herein designated due to the unknown whereabouts of the original holotype. Manahunca silhavyi Avram, 1977, is regarded as a new junior subjective synonym of M. bielawskii. In addition, two new species of Manahunca are described, M. turquino Alegre, Gainett Giribet, n. sp. and M. matazon Alegre, Gainett Giribet, n. sp. based on additional specimens from eastern Cuba, for which we provide new data on their geographical distribution, intraspecific variability and habitat. A new diagnosis and emended geographic distribution of the known species of Manahunca are provided, with hints on the current conservation status. The sexually dimorphic glandular structures found on the metatarsus III of males are explored for taxonomic significance in ten species of Stenostygninae. The existence of male dimorphism, most evident in the robustness of the chelicerae, is reported for two of the studied Manahunca species.

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The genus Gonyleptellus Roewer, 1930 is revised and reordered; a new species Gonyleptellus angeloi sp. nov. is described from Nova Friburgo, Rio de Janeiro, three additional species are transferred from other genera and one species is removed, resulting in five species in this genus. The following nomenclatural acts are proposed herein: Gonyleptes pustulatus Sørensen, 1884 is transferred from Gonyleptes to Gonyleptellus; Gonyleptes cancellatus Roewer, 1917 and Progonyleptoides pustulosus Mello-Leitão, 1935, both currently under the synonymy of Gonyleptellus bimaculatus (Sørensen, 1884), are revalidated and transferred to Gonyleptellus. Stephanocranion bimaculatus Mello-Leitão, 1931, previously considered a junior synonym of Gonyleptes cancellatus Roewer, 1917, and thereby previously carried under the synonymy of Gonyleptes bimaculatus Sørensen, 1884, is here unlinked with the former but kept under the synonymy of the latter (of which it is also a junior secondary homonym). Stephanocranion serrulatum Mello-Leitão, 1940, currently under the synonymy of G. bimaculatus, is newly synonymized with P. pustulosus. Stephanocranion bufoninus Mello-Leitão, 1949 (currently combined under Gonyleptellus) is considered a junior subjective synonym of Discocyrtus crenulatus Roewer, 1913. The male of Gonyleptellus bimaculatus is described for the first time. The genus Gonyleptellus is restricted to the states of Rio de Janeiro and São Paulo, Brazil. A key and a map for all the five valid species are presented.

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Sexual differences in morphology can evolve by sexual selection and/or natural selection. In some species, only males have morphological structures that are used as weapons. Since some weapons may also be used for defensive purposes, males and females may behave differently towards predators. In some species of harvestmen (Arachnida and Opiliones), males have sharp apophyses ("spines") on their 4th pair of legs whereas females lack them. Those apophyses are used in male-male fights and in antipredatory behaviors. The harvestmen antipredatory repertory also encompasses passive defenses such as thanatosis (death feigning), retaliation (attack on predators), and chemical defense. Due to the sexual differences on weaponry, we hypothesized that males and females of Mischonyx cuspidatus (Gonyleptidae) rely on different defensive strategies. We experimentally induced males and females to perform 3 defensive behaviors: thanatosis, pinching with legs, and chemical release. We predicted that females would engage more in passive and chemical defenses than males, whereas males would rely more on retaliation than females. As expected, females performed thanatosis more often than males. Likewise, males performed retaliation more often than females. We did not find differences in the rate of chemical defense use between the sexes. This study provides evidence that due to sexual dimorphism, alternative antipredatory behaviors may have been selected in the different sexes in M. cuspidatus.

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BACKGROUND: We present a dataset with information from the Opiliones collection of the Museu Paraense Emílio Goeldi, Northern Brazil. This collection currently has 6,400 specimens distributed in 13 families, 30 genera and 32 species and holotypes of four species: Imeri ajuba Coronato-Ribeiro, Pinto-da-Rocha & Rheims, 2013, Phareicranaus patauateua Pinto-da-Rocha & Bonaldo, 2011, Protimesius trocaraincola Pinto-da-Rocha, 1997 and Sickesia tremembe Pinto-da-Rocha & Carvalho, 2009. The material of the collection is exclusive from Brazil, mostly from the Amazon Region. The dataset is now available for public consultation on the Sistema de Informação sobre a Biodiversidade Brasileira (SiBBr) (https://ipt.sibbr.gov.br/goeldi/resource?r=museuparaenseemiliogoeldi-collection-aracnologiaopiliones). SiBBr is the Brazilian Biodiversity Information System, an initiative of the government and the Brazilian node of the Global Biodiversity Information Facility (GBIF), which aims to consolidate and make primary biodiversity data available on a platform (Dias et al. 2017). NEW INFORMATION: Harvestmen or Opiliones constitute the third largest arachnid order, with approximately 6,500 described species. Brazil is the holder of the greatest diversity in the world, with more than 1,000 described species, 95% (960 species) of which are endemic to the country. Of these, 32 species were identified and deposited in the collection of the Museu Paraense Emílio Goeldi.

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The generic name Paecilaema C.L. Koch, 1839 is anchored to the nomen dubium Cosmetus u-flavum Perty, 1833, and the fixation of the latter is proposed by designating a neotype. The choice was made on a potential topotype, being a common species in metropolitan Rio de Janeiro city, SE Brazil, which has been described as new five times and is currently best known as Metavononoides bellus (Mello-Leitão, 1932). Cosmetus u-flavum has been originally included in Paecilaema along with Paecilaema limbatum Kollar in C.L. Koch, 1839, the latter here synonymized with the former. Therefore, our choice of this species is adequate in conveying Koch's original concept of Paecilaema. The most striking diagnostic feature of the species of Paecilaema is the presence of a lyra, a unique shape of blots in layers of shades of white to pale yellow on the dorsal scutum. Other patterns of scutal white blots are hereby defined and named. Paecilaema is here considered most closely related to Metavononoides Roewer, 1928. Comments are made on the diagnostic characters and the terminology of parts of the lyra is expanded with the introduction of new terms. Comments are made on the formation of the generic name Paecilaema. Taxonomic adjustments are made in the closest relatives of Paecilaema u-flavum, and the following nomenclatural acts are proposed: (1) MNRJ 3433 is designated as male neotype of Cosmetus u-flavum, type species of Paecilaema. (2) Proposed new synonymies: Poecilaema soerenseni Henriksen, 1932 = Paecilaemula bella Mello-Leitão, 1932 = Eucynorta brasiliensis Mello-Leitão, 1923 = Paecilaema limbatum Kollar in C.L. Koch, 1839 = Cosmetus u-flavum Perty, 1833. (3) Nine species originally described elsewhere but currently placed in Metavononoides are transferred to Paecilaema, either as new or as restored combinations: Paecilaemula albisecta Mello-Leitão, 1942, Poecilaemula albosigillata Mello-Leitão, 1941, Paecilaema lyra Sørensen, 1932, Metavononoides melanacanthus Ferreira, Pedroso Kury, 2005, Paecilaema muticum Sørensen, 1932, Paecilaema ornatissimum Mello-Leitão 1942, Poecilaemula peculiare Roewer, 1917, Paecilaemula preciosa Roewer 1928 and Metavononoides renneri Ferreira, Pedroso Kury, 2007. (4) The following genera, currently in the synonymy of Paecilaema, are all revalidated and given emended diagnoses: Meterginoides Roewer, 1912, Meterginulus Roewer, 1912, Paecilaemella Roewer, 1925, Pararhauculus Roewer, 1933, Soaresella Goodnight Goodnight 1947. (5) Their respective type species, currently combined under Paecilaema, are transferred back to their revalidated genera: Paecilaema rastelliferum Pickard-Cambridge 1905 to Meterginulus; Meterginus inermis Banks, 1909 to Meterginoides; Pararhauculus lineatus Roewer, 1933 to Pararhauculus; Paecilaemella festae Roewer, 1925 to Paecilaemella and Soaresella gracilis Goodnight Goodnight, 1947 to Soaresella.

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In Brazil, the order Opiliones has been well studied, making this country the leader in research with the group, but few extensive works have been made on the distribution of harvestmen associated with caves. In this context, the present paper aims to list all records of the superfamily Gonyleptoidea associated with Brazilian caves, using records from the literature and unreported data from scientific collections. The compiled checklist contains the largest number of harvestmen species recorded for caves in one country, worldwide. A total of 155 species belonging to 7 families were recorded from 952 caves throughout 152 municipalities and 17 states of Brazil. A considerable number of 46 putative (undescribed) new species were recognized, including 9 troglomorphic species. Additionally, 161 new municipal records where found for 58 known species. The most diverse family was Gonyleptidae (104 spp.), with the subfamilies Pachylinae (55 spp.), followed by Goniosomatinae (18 spp.) and Mitobatinae (16 spp.). The number of described species analysed in the present work represents about 12% of the Brazilian opiliofauna of Gonyleptoidea, with many species widely distributed, being indicative of affinity of the group with the cave environments. Thus, the compilation of distribution data of such species (mainly the troglobitic and troglomorphic) can directly contribute to a higher valuation of their habitats, leading to better preservation policies, as well as being useful for future ecological and biogeographical studies.

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As part of an ongoing revision of the largest gonyleptid subfamily, Pachylinae, we examined Juticus furcidens Roewer, 1943. This is an elusive species mentioned only in catalogues after its description. In this paper, we redescribe it according to modern standards, including its male genitalia for the first time, which exhibit typical features of the gonyleptid K92 clade. Considering also other features from the body and appendages, we transfer J. furcidens to Gonyleptinae, and we discuss its relationships with other Gonyleptinae sensu stricto. In addition, we present a new record besides those of the type material, clarifying the hitherto imprecise distribution.

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A new species, Eucynorta rooneyi sp. nov. (Opiliones, Cosmetidae), is described from Parque Nacional Cusuco, Cortés, Honduras, a tropical montane cloud forest habitat. This is the thirty-fifth species of Eucynorta Roewer, 1912, and is characterized by the combination of three sexually dimorphic characters in males: enlarged chelicerae, some armature on femur III and IV, and swollen basitarsi on leg I. This new species is distinct from other Eucynorta species due to its unique pattern of yellow markings on area I of the dorsal scutum, and unarmed free tergites with line markings.

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