The rediscovery of a relict unlocks the first global phylogeny of whip spiders (Amblypygi).

Asymmetrical rates of cladogenesis and extinction abound in the Tree of Life, resulting in numerous minute clades that are dwarfed by larger sister groups. Such taxa are commonly regarded as phylogenetic relicts or "living fossils" when they exhibit an ancient first appearance in the fossil record and prolonged external morphological stasis, particularly in comparison to their more diversified sister groups. Due to their special status, various phylogenetic relicts tend to be well-studied and prioritized for conservation. A notable exception to this trend is found within Amblypygi ("whip spiders"), a visually striking order of functionally hexapodous arachnids that are notable for their antenniform first walking leg pair (the eponymous "whips"). Paleoamblypygi, the putative sister group to the remaining Amblypygi, is known from Late Carboniferous and Eocene deposits, but is survived by a single living species, Paracharon caecus Hansen, 1921, that was last collected in 1899. Due to the absence of genomic sequence-grade tissue for this vital taxon, there is no global molecular phylogeny for Amblypygi to date, nor a fossil-calibrated estimation of divergences within the group. Here, we report a previously unknown species of Paleoamblypygi from a cave site in Colombia. Capitalizing upon this discovery, we generated the first molecular phylogeny of Amblypygi, integrating ultraconserved element sequencing with legacy Sanger datasets and including described extant genera. To quantify the impact of sampling Paleoamblypygi on divergence time estimation, we performed in silico experiments with pruning of Paracharon. We demonstrate that the omission of relicts has a significant impact on the accuracy of node dating approaches that outweighs the impact of excluding ingroup fossils, which bears upon the ancestral range reconstruction for the group. Our results underscore the imperative for biodiversity discovery efforts in elucidating the phylogenetic relationships of "dark taxa", and especially phylogenetic relicts in tropical and subtropical habitats. The lack of reciprocal monophyly for Charontidae and Charinidae leads us to subsume them into one family, Charontidae, new synonymy.

Complete phylogeny of Micrathena spiders suggests multiple dispersal events among Neotropical rainforests, islands and landmasses, and indicates that Andean orogeny promotes speciation.

The Neotropical region is the most diverse on the planet, largely owing to its mosaic of tropical rainforests. Multiple tectonic and climatic processes have been hypothesized to contribute to generating this diversity, including Andean orogeny, the closure of the Isthmus of Panama, the GAARlandia land bridge and historical connections among currently isolated forests. Micrathena spiders are diverse and widespread in the region, and thus a complete phylogeny of this genus allows the testing of hypotheses at multiple scales. We estimated a complete, dated phylogeny using morphological data for 117 Micrathena species and molecular data of up to five genes for a subset of 79 species. Employing eventc-based approaches and biogeographic stochastic mapping while considering phylogenetic uncertainty, we estimated ancestral distributions, the timing and direction of dispersal events and diversification rates among areas. The phylogeny is generally robust, with uncertainty in the position of some of the species lacking sequences. Micrathena started diversifying around 25 Ma. Andean cloud forests show the highest in-situ speciation, while the Amazon is the major dispersal source for adjacent areas. The Dry Diagonal generated few species and is a sink of diversity. Species exchange between Central and South America involved approximately 23 dispersal events and started ~20 Ma, which is consistent with a Miocene age for the Isthmus of Panama closure. We inferred four dispersal events from Central America to the Antilles in the last 20 Myr, indicating the spiders did not reach the islands through the GAARlandia land bridge. We identified important species exchange routes among the Amazon, Andean cloud forests and Atlantic forests during the Plio-Pleistocene. Sampling all species of the genus was fundamental to the conclusions above, especially in identifying the Andean forests as the area that generated the majority of species. This highlights the importance of complete taxonomic sampling in biogeographic studies.

Organization and behavior of the synaptonemal complex during achiasmatic meiosis of four buthid scorpions.

Testicular cells of 4 buthid scorpions, Rhopalurus agamemnon (2n = 28), R. rochai (2n = 28), Tityus bahiensis (2n = 6), and T. fasciolatus (2n = 14), which show different types of chromosomal configurations in meiosis I, were subjected to cellular microspreading in order to (1) obtain knowledge about the organization and behavior of the synaptonemal complex (SC), and (2) acquire data about the mechanisms responsible for inter- and intraindividual chromosomal variation within Buthidae. Ultrastructural analysis of microspread nuclei revealed SCs with a well-preserved structure until late substages of prophase I, but did not detect kinetochore plates and recombination nodules. Pachytene cells of R. agamemnon, R. rochai and T. bahiensis exhibited single and unsynapsed axes continuous with totally synapsed SCs, indicating the occurrence of heterozygous chromosomal rearrangements. Although chromosome chains were not observed in T. fasciolatus, the presence of gaps and interlocks points out that this species also carries heterozygous rearrangements, involving a small chromosome segment. Especially in R. rochai, the cellular microspreading analysis was useful to clarify the origin of inter- and intraindividual variation in the number of bivalent-like elements and in the number of chromosomes involved in multivalent associations. It was found that more chromosomes were involved in rearrangements than previously established through investigations using light microscopy alone.

Two new species of Fernandezina Birabn, 1951 (Araneae, Palpimanidae) from cave and epigean habitats in Brazil.

The South American palpimanid genus Fernandezina Birabn currently comprises 15 described species, all known from epigean environments. Representatives of Fernandezina are easily recognized by the unexpanded femora I in both sexes and by the dorsally extended opisthosomal scutum in males. Herein, F. fernandoi sp. nov. is described based on males and females from hypogean environments and F. angeloi sp. nov. is described based on a single male from a nearby epigean environment, both in Brazil. Additionally, we provide an identification key for the species of the genus.

Thriving in dry conditions: on the Neotropical spider genus Galapa (Araneae: Pholcidae).

The genus Galapa Huber, 2000 includes tiny spiders (body length <1.5 mm) restricted to semi-arid habitats. It has long been thought to be endemic to the Galapagos Islands until G. spiniphila Huber, 2020 was described from the Venezuelan Paraguan Peninsula. Here, we support this generic assignment with molecular (CO1) data and describe two new species from Colombia (G. gabito Huber sp. n.) and Costa Rica (G. murphyi Huber sp. n.), showing that the genus is actually widely distributed. Distribution modelling identifies several high suitability areas for Galapa, all of which are poorly sampled with respect to Pholcidae (ranging from Nicaragua to northern Peru and Guiana). Our results suggest a strong sampling bias against spiders restricted to dry tropical regions and habitats.

A new species of the genus Gaucha Mello-Leito, 1924 from Minas Gerais, Brazil (Solifugae, Mummuciidae).

A new sun-spider species of the ibirapemussu species-group of the genus Gaucha is described based on males and a female collected in Southeastern Brazil. The newly described species can be readily distinguished from its congeners by the reduction of the cheliceral fixed finger, distal tooth (FD), closely positioned and smaller than the medial tooth (FM); the presence of cheliceral fixed finger profondal subproximal (PFSP) and retrofondal submedial (RFSM) teeth; and by the cheliceral movable finger, medial tooth (MM) well developed, larger than submedial tooth (MSM) and smaller than proximal tooth (MP). This is the thirteenth described species in the genus Gaucha, all known from South America.

On the sun-spiders of the ibirapemussu species-group of the genus Gaucha Mello-Leitão, 1924 (Solifugae, Mummuciidae), with description of a new species.

A new solifuge species in the genus Gaucha Mello-Leitão, 1924 and the ibirapemussu species-group is herein described based on males and females collected at Itacuruba, State of Pernambuco, and Jaicós, State of Piauí, both in Northeastern Brazil. Males of the new species can be readily recognized by having the movable finger MM and MSM teeth reduced and of similar size. The present finding raises to twelve the number of described species in the genus, five of which belong to the ibirapemussu species-group. Besides, a new locality record for the species Gaucha ibirapemussu (Carvalho et al., 2010) is here presented, along with an updated identification key for all Gaucha species.

Filling the gaps: descriptions of unnamed species included in the latest molecular phylogeny of Pholcidae (Araneae).

This paper provides formal descriptions of some of the unnamed taxa that were included in the most recent molecular phylogeny of pholcid spiders (Eberle et al. 2018, BMC Evolutionary Biology, 18, 141). The focus is on new genera and on species that belong to recently revised genera. Eight new genera and 25 new species are formally described. In Arteminae, three new species are described in Artema Walckenaer, 1837: A. bahla sp. n., A. ghubrat sp. n., and A. dhofar sp. n. (all from Oman); five new species in Arnapa gen. n. (eastern Indonesia and New Guinea): A. arfak sp. n., A. tinoor sp. n., A. manokwari sp. n., A. meja sp. n., A. tolire sp. n.; and one new species in Chisosa Huber, 2000: C. caquetio sp. n. (Netherlands Antilles). In Ninetinae, three new monotypic genera are described: Pemona gen. n., with the type species P. sapo sp. n. (Venezuela); Pinocchio gen. n., with the type species P. barauna sp. n. (Brazil); and Magana gen. n., with the type species M. velox sp. n. (Oman). In Modisiminae, three new species are described in Chibchea Huber, 2000 (all from Brazil): C. amapa sp. n., C. santosi sp. n., and C. hamadae sp. n.; one new species in Psilochorus Simon, 1893: P. bromelicolus sp. n. (Brazil); and three new monotypic genera, all from Brazil: Arenita gen. n., with the type species A. fazendinha sp. n.; Kairona gen. n., with the type species K. selva sp. n.; and Saciperere gen. n., with the type species S. catuaba sp. n. In Pholcinae, a new monotypic genus is described: Giloloa gen. n., with the type species G. sofifi sp. n. (Indonesia); three new species in the genus Aetana Huber, 2005 (all from Indonesia): A. ternate sp. n.; A. mokwam sp. n.; A. ondawamei sp. n.; and two new species in the genus Panjange Deeleman-Reinhold Deeleman, 1983 (both from Indonesia): P. thomi sp. n., and P. togutil sp. n.        Artema ghubrat is a cave-dwelling species and the only (slightly) troglomorphic representative of Arteminae; A. dhofar is presumably the closest known relative of the pantropical and synanthropic A. atlanta. The new genus Arnapa is probably species rich in eastern Indonesia and New Guinea but poorly collected; its morphological delimitation from other Australasian Arteminae (Wugigarra Huber, 2001; Holocneminus Berland, 1942; Trichocyclus Simon, 1908) needs further study. Arnapa nigromaculatus (Kulczynski, 1911) comb. n. is newly transferred from Psilochorus. Pemona sapo is the first representative of Ninetinae from Venezuela. The genus Chibchea, previously known from the Andes only, is for the first time recorded from Brazil/lowland Amazonia. Arenita fazendinha is among the few species in Pholcidae with extremely reduced procursus and barely modified male chelicerae. Kairona selva is unique among Pholcidae for its brush of strong hairs on a median horn anteriorly on the ocular area. Saciperere catuaba is one of only four pholcid species currently known to occur both in the Amazon and in the Atlantic Forest; however, variation indicates that more than one species might be included. It is among the few spiders known to have asymmetric genitalia (antisymmetric female internal genitalia). The Brazilian Psilochorus bromelicolus is the first South American Psilochorus of which both sexes are adequately described; however, the assignment to Psilochorus is tentative. Aetana ternate has extremely elongated procursi and accordingly elongated female internal genitalia. Aetana ondawamei and A. mokwam have almost identical male pedipalps and chelicerae (except for size) but differ clearly in the female genitalia.

More on the spider genus Xeropigo O.P.-Cambridge (Araneae, Corinnidae, Corinninae): seven new species and new records from Brazil.

Seven new species of the spider genus Xeropigo O. P.-Cambridge are described from Brazil, increasing the genus member list up to 16 species. X. piripiri n. sp., X. aitatu n. sp., and X. cajuina n. sp. are described from the state of Piauí. X. crispim n. sp. is described from the states of Ceará, Piauí, and Maranhão. X. oxente n. sp. is described from the state of Rio Grande do Norte. X. canga n. sp. is described from the state of Minas Gerais. X. ufo n. sp. is described from the state of Mato Grosso. The geographical distribution of X. tridentiger, X. camilae, X. pachitea, and X. perene is updated. A key to all species of Xeropigo is presented and possible relationships among all species of the genus are discussed.

Climatic Variables Do Not Directly Predict Spider Richness and Abundance in Semiarid Caatinga Vegetation, Brazil.

Spiders are abundant in tropical ecosystems and exert predatory pressure on a wide variety of invertebrate populations and also serve as prey for many others organisms, being part of complex interrelationships influenced directly and indirectly by a myriad of factors. We examined the influence of biotic (i.e., prey availability) and abiotic (i.e., temperature, precipitation, relative humidity, real evapotranspiration) factors on species richness and abundance during a two-year period in the semiarid Caatinga vegetation in northeastern Brazil. Data were analyzed through partial autocorrelation functions, cross correlations, and a path analysis. A total of 2522 spiders were collected with beating tray, pit-fall traps, and malaise traps, comprising 91 species and 34 families. Spider abundance peaked in the rainy season. Our results suggest that total invertebrate abundance has a direct influence on spider richness and abundance, whereas the effects of precipitation were mainly indirectly related to most spider assemblage parameters. The increase in vegetation cover with the rainy season in the Caatinga provides more breeding and foraging sites for spiders and stimulates their activities. Additionally, rainfall in arid and semiarid ecosystems stimulated the activity and reproduction of many herbivore and detritivore invertebrates dependent on plant biomass and necromass consumption, leading to an increase in spider prey availability.