Studies in evolutionary biology and biogeography increasingly rely on the estimation of dated phylogenetic trees using molecular clocks. In turn, the calibration of such clocks is critically dependent on external evidence (i.e. fossils) anchoring the ages of particular nodes to known absolute ages. In recent years, a plethora of new fossil spiders, especially from the Mesozoic, have been described, while the number of studies presenting dated spider phylogenies based on fossil calibrations increased sharply. We critically evaluate 44 of these studies, which collectively employed 67 unique fossils in 180 calibrations. Approximately 54% of these calibrations are problematic, particularly regarding unsupported assignment of fossils to extant clades (44%) and crown (rather than stem) dating (9%). Most of these cases result from an assumed equivalence between taxonomic placement of fossils and their phylogenetic position. To overcome this limitation, we extensively review the literature on fossil spiders, with a special focus on putative synapomorphies and the phylogenetic placement of fossil species with regard to their importance for calibrating higher taxa (families and above) in the spider tree of life. We provide a curated list including 41 key fossils intended to be a basis for future estimations of dated spider phylogenies. In a second step, we use a revised set of 23 calibrations to estimate a new dated spider tree of life based on transcriptomic data. The revised placement of key fossils and the new calibrated tree are used to resolve a long‐standing debate in spider evolution – we tested whether there has been a major turnover in the spider fauna between the Mesozoic and Cenozoic. At least 17 (out of 117) extant families have been recorded from the Cretaceous, implying that at least 41 spider lineages in the family level or above crossed the Cretaeous–Paleogene (K–Pg) boundary. The putative phylogenetic affinities of families known only from the Mesozoic suggest that at least seven Cretaceous families appear to have no close living relatives and might represent extinct lineages. There is no unambiguous fossil evidence of the retrolateral tibial apophysis clade (RTA‐clade) in the Mesozoic, although molecular clock analyses estimated the major lineages within this clade to be at least ∼100 million years old. Our review of the fossil record supports a major turnover showing that the spider faunas in the Mesozoic and the Cenozoic are very distinct at high taxonomic levels, with the Mesozoic dominated by Palpimanoidea and Synspermiata, while the Cenozoic is dominated by Araneoidea and RTA‐clade spiders.

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Gnaphosidae Pocock are a very diverse spider family with remarkable spinning organ morphology. Although the family has received intense taxonomic attention in recent years, its intergeneric relationships remain obscure. A phylogenetic analysis of Gnaphosidae genera was performed to untangle the evolutionary history of the family. A matrix of 324 morphological characters, scored for 71 gnaphosid genera and 29 outgroup taxa, was analysed through parsimony and Bayesian phylogenetic inference. Gnaphosidae are not recovered as a monophyletic group, neither were most of the previously proposed intrafamiliar groupings. In accordance with the phylogenetic results obtained, Vectius Simon and Hemicloea Thorell are transferred to Trochanteriidae, and Xenoplectus Schiapelli & Gerschman de Pikelin to Liocranidae. Micaria Westring, Nauhea Forster and Verita Ram ırez & Grismado (and some related genera) are probably not gnaphosids, although their phylogenetic placement is uncertain. Gnaphosidae s.s. are defined as spiders with enlarged piriform gland spigots, longer and wider than the major ampullate gland spigots. Within Gnaphosidae s.s., well-supported clades allow the redefinition, on the basis of quantitative phylogenetic evidence, of Gnaphosinae Pocock, Zelotinae Platnick, Herpyllinae Platnick, Drassodinae Simon, Prodidominae Simon rank res. and the newly proposed Leptodrassinae subfam. nov. Many genera are not assigned to subfamily given their poorly supported and unstable relationships. The homology and evolution of structures such as the claw tuft clasper, the spinning organs and the modification of cheliceral promargin are discussed.

The current biodiversity crisis makes the quantification of the diversity and the description of organism distribution particularly pressing. Biological inventories are among the most effective ways to improve the knowledge about local biota, but they can be very time and money‐consuming. The determination of adequate sampling effort and the selection of cost‐effective collecting methods are critical issues. In this article, a spider diversity inventory in an Atlantic semi‐deciduous forest fragment in Brazil was used to compare the efficiency of three collecting methods in two different seasons in order to propose an optimised sampling protocol. The worthiness of increasing sampling effort in the target area and similar tropical ecosystems was estimated and evaluated in terms of its cost‐effectiveness. For a better sampling of the spider community, it is suggested that a proportion of 55, 29 and 16% of total sampling hours should be dedicated to nocturnal hand collecting (NHC), pitfall traps and beating trays, respectively, in the rainy season. If only one method can be applied, the most efficient in terms of species per sampling is the NHC. A completeness of 70% of the estimated spider species richness (as predicted by the Chao1 estimator) was observed in the complete inventory and increasing sampling effort in the studied area may be highly ineffective when the costs involved are considered. Other studies in similar tropical rainforest areas also presented completeness around 70%, which might be a threshold from which the sampling effort necessary to raise the observed species richness substantially starts to be ineffective.

Understanding diversity has been a pursuit in evolutionary biology since its inception. A challenge arises when sexual selection has played a role in diversification. Questions of what constitutes a ‘species’, homoplasy vs. synapomorphy, and whether sexually selected traits show phylogenetic signal have hampered work on many systems. Peacock spiders are famous for sexually selected male courtship dances and peacock-like abdominal ornamentation. This lineage of jumping spiders currently includes over 90 species classified into two genera, Maratus and Saratus. Most Maratus species have been placed into groups based on secondary sexual characters, but evolutionary relationships remain unresolved. Here we assess relationships in peacock spiders using phylogenomic data (ultraconserved elements and RAD-sequencing). Analyses reveal that Maratus and the related genus Saitis are paraphyletic. Many, but not all, morphological groups within a ‘core Maratus’ clade are recovered as genetic clades but we find evidence for undocumented speciation. Based on original observations of male courtship, our comparative analyses suggest that courtship behaviour and peacock-like abdominal ornamentation have evolved sequentially, with some traits inherited from ancestors and others evolving repeatedly and independently from ‘simple’ forms. Our results have important implications for the taxonomy of these spiders, and provide a much-needed evolutionary framework for comparative studies of the evolution of sexual signal characters.

The American gnaphosid genus Apopyllus Platnick & Shadab is found from southern Mexico to southern Argentina. It can be diagnosed by the complex shape of the RTA, by the membranous tegular extension, the long coiled embolus, the retrolateral incision on the cymbium, the long convoluted copulatory duct extending anteriorly to the copulatory openings and by the presence of paramedian epigynal pockets and of an anterior ridge on the epigynum. The RTA characters are important in species taxonomy but the complex shape and variation of the RTA hampers identification, especially regarding the two most common species: A. suavis (Simon) and A. silvestrii (Simon). In this paper the genus is revised, the genital morphology is described, and homology between its components and those of other genera is discussed. Apopyllus suavis is considered a senior synonym of Apopyllus pauper (Mello-Leitão) and A. iheringi (Mello-Leitão). Four new species are described from Brazil: A. aeolicus, A. atlanticus, A. centralis and A. gandarela.

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Aim Fossil data may be crucial to infer biogeographical history, especially in taxa with tropical trans‐Pacific distributions. Here, we use extinct and extant trochanteriid flattened spiders to test hypotheses that could explain its trans‐Pacific disjunct distribution, including a Boreotropical origin with a North Atlantic dispersal, an African origin with South Atlantic dispersal and an Eurasian origin with Bering Bridge route. Location World‐wide. Taxon Trochanteriidae, Plator‐Doliomalus‐Vectius (PDV) clade. Methods MicroCT was used to collect morphological data from an undescribed Baltic amber fossil. These data were used with additional fossils and extant species in a total‐evidence, tip‐dated phylogenetic analysis. We tested different scenarios using constrained dispersal matrices in a Bayesian approach. An analysis with fossils pruned was also performed to explore how lack of fossil data might impact inferences of biogeographical process. Results The phylogenetic analyses allowed us to place the new fossil in the genus Plator. Analyses without fossils suggest an African origin with a dispersal to Asia from India and a South Atlantic dispersal to South America. When fossils are included, hypothesis‐testing rejects this scenario and equally supports a Boreotropical and an Afro‐European origin with a South Atlantic route and a dispersal to Asia from Europe. Main conclusions Biogeographical inferences of disjunctly distributed taxa should be interpreted with caution when fossils are not included. Although one alternative hypothesis was not completely rejected, results show that the Boreotropical hypothesis for the PDV clade could be a robust explanation for its actual distribution. This hypothesis is mostly overlooked in animal taxa and rigorous tests with other taxa with similar distributions may reveal that a Boreotropical origin is common. We discuss methodological approaches that could improve biogeographical tests using fossils as terminals.