Tightening the requirements for species diagnoses would help integrate DNA-based descriptions in taxonomic practice.

Modern advances in DNA sequencing hold the promise of facilitating descriptions of new organisms at ever finer precision but have come with challenges as the major Codes of bionomenclature contain poorly defined requirements for species and subspecies diagnoses (henceforth, species diagnoses), which is particularly problematic for DNA-based taxonomy. We, the commissioners of the International Commission on Zoological Nomenclature, advocate a tightening of the definition of "species diagnosis" in future editions of Codes of bionomenclature, for example, through the introduction of requirements for specific information on the character states of differentiating traits in comparison with similar species. Such new provisions would enhance taxonomic standards and ensure that all diagnoses, including DNA-based ones, contain adequate taxonomic context. Our recommendations are intended to spur discussion among biologists, as broad community consensus is critical ahead of the implementation of new editions of the International Code of Zoological Nomenclature and other Codes of bionomenclature.

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.

Rapid divergent evolution of internal female genitalia and the coevolution of male genital morphology revealed by micro-computed tomography.

Animal genitalia are thought to evolve rapidly and divergently in response to sexual selection. Studies of genital evolution have focused largely on male genitalia. The paucity of work on female genital morphology is probably due to problems faced in quantifying shape variation, due to their composition and accessibility. Here we use a combination of micro-computed tomography, landmark free shape quantification and phylogenetic analysis to quantify the rate of female genital shape evolution among 29 species of Antichiropus millipedes, and their coevolution with male genitalia. We found significant variation in female and male genital shape among species. Male genital shape showed a stronger phylogenetic signal than female genital shape, although the phylogenetic signal effect sizes did not differ significantly. Male genital shape was found to be evolving 1.2 times faster than female genital shape. Female and male genital shape exhibited strong correlated evolution, indicating that genital shape changes in one sex are associated with corresponding changes in the genital shape of the other sex. This study adds novel insight into our growing understanding of how female genitalia can evolve rapidly and divergently, and highlights the advantages of three-dimensional techniques and multivariate analyses in studies of female genital evolution.

A comprehensive molecular phylogeny of the terrestrial Parasitengona (Acariformes, Prostigmata) provides insights into the evolution of their metamorphosis, invasion into aquatic habitats and classification.

Parasitengona (velvet mites, chiggers and water mites) is a highly diverse and globally distributed mite lineage encompassing over 11,000 described species, inhabiting terrestrial, freshwater and marine habitats. Certain species, such as chiggers (Trombiculidae), have a great medical and veterinary importance as they feed on their vertebrate hosts and vector pathogens. Despite extensive previous research, the classification of Parasitengona is still contentious, particularly regarding the boundaries between superfamilies and families, exacerbated by the absence of a comprehensive phylogeny. The ontogeny of most Parasitengona is distinct by the presence of striking metamorphosis, with parasitic larvae being heteromorphic compared to the predatory free-living deutonymphs and adults. The enigmatic superfamily Allotanaupodoidea is an exception, with larvae and active post-larval stages being morphologically similar, suggesting that the absence of metamorphosis may be either an ancestral state or a secondary reversal. Furthermore, there is disagreement in the literature on whether Parasitengona had freshwater or terrestrial origin. Here, we inferred phylogenetic relationships of Parasitengona (89 species, 36 families) and 307 outgroups using five genes (7,838 nt aligned). This phylogeny suggests a terrestrial origin of Parasitengona and a secondary loss of metamorphosis in Allotanaoupodoidea. We recovered the superfamily Trombidioidea (Trombidioidea sensu lato) as a large, well-supported, higher-level clade including 10 sampled families. We propose a new classification for the terrestrial Parasitengona with three new major divisions (epifamilies) of the superfamily Trombidioidea: Trombelloidae (families Audyanidae, Trombellidae, Neotrombidiidae, Johnstonianidae, Chyzeriidae); Trombidioidae (Microtrombidiidae, Neothrombiidae, Achaemenothrombiidae, Trombidiidae, Podothrombiidae); and Trombiculoidae (=Trombiculidae sensu lato). Adding them to previously recognized superfamilies Allotanaupodoidea, Amphotrombioidea, Calyptostomatoidea, Erythraeoidea, Tanaupodoidae and Yurebilloidae.

Comprehensive Species Sampling and Sophisticated Algorithmic Approaches Refute the Monophyly of Arachnida.

Deciphering the evolutionary relationships of Chelicerata (arachnids, horseshoe crabs, and allied taxa) has proven notoriously difficult, due to their ancient rapid radiation and the incidence of elevated evolutionary rates in several lineages. Although conflicting hypotheses prevail in morphological and molecular data sets alike, the monophyly of Arachnida is nearly universally accepted, despite historical lack of support in molecular data sets. Some phylotranscriptomic analyses have recovered arachnid monophyly, but these did not sample all living orders, whereas analyses including all orders have failed to recover Arachnida. To understand this conflict, we assembled a data set of 506 high-quality genomes and transcriptomes, sampling all living orders of Chelicerata with high occupancy and rigorous approaches to orthology inference. Our analyses consistently recovered the nested placement of horseshoe crabs within a paraphyletic Arachnida. This result was insensitive to variation in evolutionary rates of genes, complexity of the substitution models, and alternative algorithmic approaches to species tree inference. Investigation of sources of systematic bias showed that genes and sites that recover arachnid monophyly are enriched in noise and exhibit low information content. To test the impact of morphological data, we generated a 514-taxon morphological data matrix of extant and fossil Chelicerata, analyzed in tandem with the molecular matrix. Combined analyses recovered the clade Merostomata (the marine orders Xiphosura, Eurypterida, and Chasmataspidida), but merostomates appeared nested within Arachnida. Our results suggest that morphological convergence resulting from adaptations to life in terrestrial habitats has driven the historical perception of arachnid monophyly, paralleling the history of numerous other invertebrate terrestrial groups.

Phylogenomics of Scorpions Reveal Contemporaneous Diversification of Scorpion Mammalian Predators and Mammal-Active Sodium Channel Toxins.

Scorpions constitute a charismatic lineage of arthropods and comprise more than 2500 described species. Found throughout various tropical and temperate habitats, these predatory arachnids have a long evolutionary history, with a fossil record that began in the Silurian. While all scorpions are venomous, the asymmetrically diverse family Buthidae harbors nearly half the diversity of extant scorpions, and all but one of the 58 species that are medically significant to humans. However, the lack of a densely sampled scorpion phylogeny has hindered broader inferences of the diversification dynamics of scorpion toxins. To redress this gap, we assembled a phylogenomic data set of 100 scorpion venom gland transcriptomes and genomes, emphasizing the sampling of highly toxic buthid genera. To infer divergence times of venom gene families, we applied a phylogenomic node dating approach for the species tree in tandem with phylostratigraphic bracketing to estimate the minimum ages of mammal-specific toxins. Our analyses establish a robustly supported phylogeny of scorpions, particularly with regard to relationships between medically significant taxa. Analysis of venom gene families shows that mammal-active sodium channel toxins (NaTx) have independently evolved in five lineages within Buthidae. Temporal windows of mammal-targeting toxin origins are correlated with the basal diversification of major scorpion mammal predators such as shrews, bats, and rodents. These results suggest an evolutionary model of relatively recent diversification of buthid NaTx homologs in response to the diversification of scorpion predators. [Adaptation; arachnids; phylogenomic dating; phylostratigraphy; venom.].

Taxonomic Sampling and Rare Genomic Changes Overcome Long-Branch Attraction in the Phylogenetic Placement of Pseudoscorpions.

Long-branch attraction is a systematic artifact that results in erroneous groupings of fast-evolving taxa. The combination of short, deep internodes in tandem with long-branch attraction artifacts has produced empirically intractable parts of the Tree of Life. One such group is the arthropod subphylum Chelicerata, whose backbone phylogeny has remained unstable despite improvements in phylogenetic methods and genome-scale data sets. Pseudoscorpion placement is particularly variable across data sets and analytical frameworks, with this group either clustering with other long-branch orders or with Arachnopulmonata (scorpions and tetrapulmonates). To surmount long-branch attraction, we investigated the effect of taxonomic sampling via sequential deletion of basally branching pseudoscorpion superfamilies, as well as varying gene occupancy thresholds in supermatrices. We show that concatenated supermatrices and coalescent-based summary species tree approaches support a sister group relationship of pseudoscorpions and scorpions, when more of the basally branching taxa are sampled. Matrix completeness had demonstrably less influence on tree topology. As an external arbiter of phylogenetic placement, we leveraged the recent discovery of an ancient genome duplication in the common ancestor of Arachnopulmonata as a litmus test for competing hypotheses of pseudoscorpion relationships. We generated a high-quality developmental transcriptome and the first genome for pseudoscorpions to assess the incidence of arachnopulmonate-specific duplications (e.g., homeobox genes and miRNAs). Our results support the inclusion of pseudoscorpions in Arachnopulmonata (new definition), as the sister group of scorpions. Panscorpiones (new name) is proposed for the clade uniting Scorpiones and Pseudoscorpiones.

One-way ticket to the blue: A large-scale, dated phylogeny revealed asymmetric land-to-water transitions in acariform mites (Acari: Acariformes).

Acariform mites are an ancient and megadiverse lineage that may have experienced a complex pattern of invasions into terrestrial and aquatic habitats. These among-realm transitions may relate to periods of turmoil in Earth's history or be simply results of uneven biodiversity patterns across habitats. Here, we inferred a dated, representative acariform phylogeny (five genes, 9,200 bp aligned, 367 terminals belonging to 150 ingroup plus 15 outgroup families, 23 fossil calibration points) which was used to infer transitions between marine/freshwater/terrestrial habitats. We detected four unambiguous transitions from terrestrial to freshwater habitats (Hydrozetes, Naiadacarus, Fusohericia, Afronothrus, Homocaligus); one from freshwater to marine (Pontarachnidae), and four from marine to brackish or freshwater transitions (all among Halacaridae: Acarothrix; Halacarellus petiti; Copidognathus sp.; clade Limnohalacarus + Soldanellonyx + Porohalacarus + Porolohmannella). One transition to the sea was inferred ambiguously with respect to the ancestor being either terrestrial or freshwater (Hyadesiidae), and another must be most carefully examined by adding potential related taxa (Selenoribatidae + Fortuyniidae). Finally, we inferred a single, remarkable transition from aquatic to terrestrial habitats involving early evolution of the large and ecologically diverse lineage: the ancestor of the Halacaridae + Parasitengona clade was probably freshwater given our dataset, thus making terrestrial Parasitengona secondarily terrestrial. Overall, our results suggested a strong asymmetry in environmental transitions: the majority occurred from terrestrial to aquatic habitats. This asymmetry is probably linked to mites' biological properties and uneven biodiversity patterns across habitats rather than Earth's geological history. Since the land holds more acariform diversity than water habitats, a shift from the former is more likely than from the latter. We inferred the following relationships: alicid endeostigmatid + eriophyoid (Alycidae, (Nanorchestidae, (Nematalycidae, Eriophyoidea))) being sister group to the remaining Acariformes: (proteonematalycid Endeostigmata, alicorhagiid Endeostigmata, Trombidiformes, Oribatida (including Astigmata)). Trombidiform relationships had several novel rearrangements: (i) traditional Eupodina lacked support for the inclusion of Bdelloidea; (ii) Teneriffidae, traditionally placed among Anystina, was consistently recovered in a clade including Heterostigmata in Eleutherengona; (iii) several lineages, such as Adamystidae, Paratydeidae, Caeculidae and Erythracaridae, were recovered in a large clade along other Anystina and Eleutherengona, suggesting single origins of several fundamental character states, such as the reduction of the cheliceral fixed digit and development of the palpal thumb-claw complex.

Diversification of the mygalomorph spider genus Aname (Araneae: Anamidae) across the Australian arid zone: Tracing the evolution and biogeography of a continent-wide radiation.

The assembly of the Australian arid zone biota has long fascinated biogeographers. Covering over two-thirds of the continent, Australia's vast arid zone biome is home to a distinctive fauna and flora, including numerous lineages which have diversified since the Eocene. Tracing the origins and speciation history of these arid zone taxa has been an ongoing endeavour since the advent of molecular phylogenetics, and an increasing number of studies on invertebrate animals are beginning to complement a rich history of research on vertebrate and plant taxa. In this study, we apply continent-wide genetic sampling and one of the largest phylogenetic data matrices yet assembled for a genus of Australian spiders, to reconstruct the phylogeny and biogeographic history of the open-holed trapdoor spider genus Aname L. Koch, 1873. This highly diverse lineage of Australian mygalomorph spiders has a distribution covering the majority of Australia west of the Great Dividing Range, but apparently excluding the high rainfall zones of eastern Australia and Tasmania. Original and legacy sequences were obtained for three mtDNA and four nuDNA markers from 174 taxa in seven genera, including 150 Aname specimen terminals belonging to 102 species-level operational taxonomic units, sampled from 32 bioregions across Australia. Reconstruction of the phylogeny and biogeographic history of Aname revealed three radiations (Tropical, Temperate-Eastern and Continental), which could be further broken into eight major inclusive clades. Ancestral area reconstruction revealed the Pilbara, Monsoon Tropics and Mid-West to be important ancestral areas for the genus Aname and its closest relatives, with the origin of Aname itself inferred in the Pilbara bioregion. From these origins in the arid north-west of Australia, our study found evidence for a series of subsequent biome transitions in separate lineages, with at least eight tertiary incursions back into the arid zone from more mesic tropical, temperate or eastern biomes, and only two major clades which experienced widespread (primary) in situ diversification within the arid zone. Based on our phylogenetic results, and results from independent legacy divergence dating studies, we further reveal the importance of climate-driven biotic change in the Miocene and Pliocene in shaping the distribution and composition of the Australian arid zone biota, and the value of continent-wide studies in revealing potentially complex patterns of arid zone diversification in dispersal-limited invertebrate taxa.

Phylogenomic interrogation resolves the backbone of the Pseudoscorpiones tree of life.

Pseudoscorpiones, with nearly 3700 described species, are an ancient and globally distributed group of arachnids with a fossil record dating back to the Middle Devonian. Previous attempts to reconstruct their phylogenetic history have used morphology or a few amplicons, mostly of rRNAs and mitochondrial genes, which have not been able to completely resolve family-level relationships nor the earliest nodes in the pseudoscorpion tree-those which are most informative about the origins of key characters like venoms and silk. Here we undertake a phylogenetic approach using 41 pseudoscorpion transcriptomes and a series of analyses that account for many of the common pitfalls faced in large phylogenomic analyses. All analyses, using concatenation methods and coalescent approaches, supported monophyly of Iocheirata (the venomous pseudoscorpions), which diversified mostly during the Mesozoic, but paraphyly of Epiocheirata, with a sister group relationship of Feaelloidea to Iocheirata, with Chthonioidea as their sister group. These three main lineages were established during the mid-to-late Paleozoic. Our phylogenetic scheme is consistent with the prior hypothesis that the lack of venom in Pseudoscorpiones is plesiomorphic and not a synapomorphy of Epiocheirata. Based on the results of this study, a new classification is proposed for Pseudoscorpiones including the following new nomenclatural and taxonomic acts: the new suborders Palaeosphyronida Harvey and Atoposphyronida Harvey for Dracochelidae and Feaelloidea, respectively; the newly recognized superfamily Garypinoidea for Garypinidae and Larcidae; the revised rank for Lechytiidae and Tridenchthoniidae, which are regarded as subfamilies of Chthoniidae; the revised rank for Tridenchthoniini and Verrucadithini which are regarded as tribes of Tridenchthoniinae; and the elevation of Hesperolpiinae as a distinct family, Hesperolpiidae.

Too hot to handle: Cenozoic aridification drives multiple independent incursions of Schizomida (Hubbardiidae) into hypogean environments.

The formation of the Australian arid zone, Australia's largest and youngest major biome, has been recognized as a major driver of rapid evolutionary radiations in terrestrial plants and animals. Here, we investigate the phylogenetic diversity and evolutionary history of subterranean short-tailed whip scorpions (Schizomida: Hubbardiidae), which are a significant faunal component of Western Australian hypogean ecosystems. We sequenced two mitochondrial (12S, COI) and three nuclear DNA markers (18S, 28S, ITS2) from ∼600 specimens, largely from the genera Draculoides and Paradraculoides, including 20 previously named species and an additional 56 newly identified operational taxonomic units (OTUs). Phylogenetic analyses revealed a large and rapid species radiation congruent with Cenozoic aridification of the continent, in addition to the identification of a new genus in Western Australia and the first epigean schizomid from the Pilbara. Here, we also synonymise Paradraculoides with Draculoides (new synonymy), due to paraphyly and a lack of reliable characters to define the two genera. Our results are consistent with multiple colonisations of the subterranean realm from epigean ancestors as their forest habitat fragmented and retracted, with ongoing fragmentation and diversification of lineages underground. These findings illustrate the remarkable diversity and high incidence of short-range endemism of Western Australia's subterranean fauna, which has important implications for identifying and managing short-range endemic subterranean fauna. They also highlight the advantages of including molecular data in subterranean fauna surveys as all specimens can be utilized, regardless of sex and life stage. Additionally, we have provided the first multi-gene phylogenetic framework for Australian schizomids, which will enable researchers and environmental consultants to identify new taxa or align them to existing lineages.

A revised dated phylogeny of scorpions: Phylogenomic support for ancient divergence of the temperate Gondwanan family Bothriuridae.

The scorpion family Bothriuridae occupies a subset of landmasses formerly constituting East and West temperate Gondwana, but its relationship to other scorpion families is in question. Whereas morphological data have strongly supported a sister group relationship of Bothriuridae and the superfamily Scorpionoidea, a recent phylogenomic analysis recovered a basal placement of bothriurids within Iurida, albeit sampling only a single exemplar. Here we reexamined the phylogenetic placement of the family Bothriuridae, sampling six bothriurid exemplars representing both East and West Gondwana, using transcriptomic data. Our results demonstrate that the sister group relationship of Bothriuridae to the clade ("Chactoidea" + Scorpionoidea) is supported by the inclusion of additional bothriurid taxa, and that this placement is insensitive to matrix completeness or partitioning by evolutionary rate. We also estimated divergence times within the order Scorpiones using multiple fossil calibrations, to infer whether the family Bothriuridae is sufficiently old to be characterized as a true Gondwanan lineage. We show that scorpions underwent ancient diversification between the Devonian and early Carboniferous. The age interval of the bothriurids sampled (a derived group that excludes exemplars from South Africa) spans the timing of breakup of temperate Gondwana.

Post-Eocene climate change across continental Australia and the diversification of Australasian spiny trapdoor spiders (Idiopidae: Arbanitinae).

The formation and spread of the Australian arid zone during the Neogene was a profoundly transformative event in the biogeographic history of Australia, resulting in extinction or range contraction in lineages adapted to mesic habitats, as well as diversification and range expansion in arid-adapted taxa (most of which evolved from mesic ancestors). However, the geographic origins of the arid zone biota are still relatively poorly understood, especially among highly diverse invertebrate lineages, many of which are themselves poorly documented at the species level. Spiny trapdoor spiders (Idiopidae: Arbanitinae) are one such lineage, having mesic 'on-the-continent' Gondwanan origins, while also having experienced major arid zone radiations in select clades. In this study, we present new orthologous nuclear markers for the phylogenetic inference of mygalomorph spiders, and use them to infer the phylogeny of Australasian Idiopidae with a 12-gene parallel tagged amplicon next-generation sequencing approach. We use these data to test the mode and timing of diversification of arid-adapted idiopid lineages across mainland Australia, and employ a continent-wide sampling of the fauna's phylogenetic and geographic diversity to facilitate ancestral area inference. We further explore the evolution of phenotypic and behavioural characters associated with both arid and mesic environments, and test an 'out of south-western Australia' hypothesis for the origin of arid zone clades. Three lineages of Idiopidae are shown to have diversified in the arid zone during the Miocene, one (genus Euoplos) exclusively in Western Australia. Arid zone Blakistonia likely had their origins in South Australia, whereas in the most widespread genus Aganippe, a more complex scenario is evident, with likely range expansion from southern Western Australia to southern South Australia, from where the bulk of the arid zone fauna then originated. In Aganippe, remarkable adaptations to phragmotic burrow-plugging in transitional arid zone taxa have evolved twice independently in Western Australia, while in Misgolas and Cataxia, burrow door-building behaviours have likely been independently lost at least three times in the eastern Australian mesic zone. We also show that the presence of idiopids in New Zealand (Cantuaria) is likely to be the result of recent dispersal from Australia, rather than ancient continental vicariance. By providing the first comprehensive, continental synopsis of arid zone biogeography in an Australian arachnid lineage, we show that the diversification of arbanitine Idiopidae was intimately associated with climate shifts during the Neogene, resulting in multiple Mio-Pliocene radiations.

A new troglomorphic species of Larca (Pseudoscorpiones, Larcidae) from Colorado.

A new species of Larca is described from dry habitats in a cave in central Colorado. Like other cave-dwelling species of Larca, the new species Larcabouldericasp. nov., shows relatively modest morphological adaptations, such as pale colouration and slightly elongated appendages, compared with their epigean counterparts. This species is the sixth cave-dwelling species of Larca described from North America and, like other cave-dwelling Larca in North America and Europe, tends to be distributed in more southerly regions.

First fossil species of family Hyidae (Arachnida: Pseudoscorpiones) confirms 99 million years of ecological stasis in a Gondwanan lineage.

Burmese amber preserves a diverse assemblage of Cretaceous arachnids, and among pseudoscorpions (Arachnida: Pseudoscorpiones), ten species in five families have already been named. Here, we describe a new fossil species from Burmese amber in the pseudoscorpion family Hyidae, providing detailed measurements, photographs and 3D-models from synchrotron scanning. Based on morphology, the new fossil, Hya fynni sp. nov. is placed in the genus Hya, and is nearly identical to extant species in the genus, except for the position of trichobothrium est on the pedipalpal chela, thereby indicating extreme morphological stasis in this invertebrate lineage over the last 99 million years. Hya fynni represents the first described fossil species in Hyidae, and the third described Burmese fossil in the superfamily Neobisioidea. It also joins the garypinid, Amblyolpium burmiticum, in representing the oldest fossil records for extant pseudoscorpion genera. Considering proposed divergence dates, the newly described fossil species bolsters a Gondwanan origin for Hyidae, and provides evidence for the "Late Jurassic Rifting" hypothesis for the Burma Terrane, in which this landmass rifted from Gondwana in the Late Jurassic and collided with Eurasia by the Cretaceous/Eocene. Like Hya species today, H. fynni likely inhabited humicolous microhabitats in tropical forests on the Burma Terrane, supporting ecological niche stasis for this family since the Mesozoic.

A novel expression domain of extradenticle underlies the evolutionary developmental origin of the chelicerate patella.

Neofunctionalization of duplicated gene copies is thought to be an important process underlying the origin of evolutionary novelty and provides an elegant mechanism for the origin of new phenotypic traits. One putative case where a new gene copy has been linked to a novel morphological trait is the origin of the arachnid patella, a taxonomically restricted leg segment. In spiders, the origin of this segment has been linked to the origin of the paralog dachshund-2 , suggesting that a new gene facilitated the expression of a new trait. However, various arachnid groups that possess patellae do not have a copy of dachshund-2 , disfavoring the direct link between gene origin and trait origin. We investigated the developmental genetic basis for patellar patterning in the harvestman Phalangium opilio , which lacks dachshund-2 . Here, we show that the harvestman patella is established by a novel expression domain of the transcription factor extradenticle . Leveraging this definition of patellar identity, we surveyed targeted groups across chelicerate phylogeny to assess when this trait evolved. We show that a patellar homolog is present in Pycnogonida (sea spiders) and various arachnid orders, suggesting a single origin of the patella in the ancestor of Chelicerata. A potential loss of the patella is observed in Ixodida. Our results suggest that the modification of an ancient gene, rather than the neofunctionalization of a new gene copy, underlies the origin of the patella. Broadly, this work underscores the value of comparative data and broad taxonomic sampling when testing hypotheses in evolutionary developmental biology.

A new genus and five new species of pseudoscorpions (Arachnida, Pseudoscorpiones, Withiidae) from Colombia.

The pseudoscorpion family Withiidae is widely distributed around the world, with most of its diversity in tropical areas. Five new species and a new genus from Colombia are described: Cystowithiusflorezisp. nov., Parawithiusbromelicolasp. nov., Oligowithiusachaguasp. nov., and the genus Paciwithiusgen. nov. with two species Paciwithiusvalduparensissp. nov. and Paciwithiuschimbilacussp. nov. A reassessment of the subgenus Dolichowithius (Oligowithius) Beier, 1936 allows the elevation to a full generic level, and the transfer of the only known species to Oligowithius, forming the new combination Oligowithiusabnormis (Beier, 1936), comb. nov.

Correlation with a limited set of behavioral niches explains the convergence of somatic morphology in mygalomorph spiders.

Understanding the drivers of morphological convergence requires investigation into its relationship with behavior and niche space, and such investigations in turn provide insights into evolutionary dynamics, functional morphology, and life history. Mygalomorph spiders (trapdoor spiders and their kin) have long been associated with high levels of morphological homoplasy, and many convergent features can be intuitively associated with different behavioral niches. Using genus-level phylogenies based on recent genomic studies and a newly assembled matrix of discrete behavioral and somatic morphological characters, we reconstruct the evolution of burrowing behavior in the Mygalomorphae, compare the influence of behavior and evolutionary history on somatic morphology, and test hypotheses of correlated evolution between specific morphological features and behavior. Our results reveal the simplicity of the mygalomorph adaptive landscape, with opportunistic, web-building taxa at one end, and burrowing/nesting taxa with structurally modified burrow entrances (e.g., a trapdoor) at the other. Shifts in behavioral niche, in both directions, are common across the evolutionary history of the Mygalomorphae, and several major clades include taxa inhabiting both behavioral extremes. Somatic morphology is heavily influenced by behavior, with taxa inhabiting the same behavioral niche often more similar morphologically than more closely related but behaviorally divergent taxa, and we were able to identify a suite of 11 somatic features that show significant correlation with particular behaviors. We discuss these findings in light of the function of particular morphological features, niche dynamics within the Mygalomorphae, and constraints on the mygalomorph adaptive landscape relative to other spiders.

A new pseudoscorpion genus (Garypinoidea: Garypinidae) from the Eocene supports extinction and range contraction in the European paleobiota.

During the Paleogene, the Holarctic experienced drastic climatic oscillations, including periods of extensive glaciation. These changes had a severe impact on both the flora and fauna causing widespread extinction and range shifts with some taxa retreating to refugia in the Mediterranean Basin. Here we provide evidence for this hypothesis using fossils from the pseudoscorpion family Garypinidae Daday, 1889 (Arachnida: Pseudoscorpiones). This family comprises 21 extant genera from all continents except Antarctica but is restricted to low mid-latitudes (<44°N) in the Northern Hemisphere. We provide the second record of garypinids from the European succinite ambers of the Eocene by describing the first extinct genus in Garypinidae, Baltamblyolpium gen. nov., which includes two species: Baltamblyolpium gizmotum sp. nov. from Baltic amber and Baltamblyolpium grabenhorsti sp. nov. from Bitterfeld amber. The new genus exhibits a morphology that closely resembles Neoamblyolpium Hoff, 1956 from western North America and the genus Amblyolpium Simon, 1898, which is widespread but includes taxa restricted to Mediterranean refugia in Europe. The discovery of a new fossil genus of Garypinidae from Europe confirms that the family was found at more northerly latitudes during the Eocene, however, extinction and range contraction resulted in their present-day relictual distribution in southern Europe like many other lineages that once thrived in the European "Baltic amber forest" of the Eocene.

A Case for Below-Ground Dispersal? Insights into the Biology, Ecology and Conservation of Blind Cave Spiders in the Genus Troglodiplura (Mygalomorphae: Anamidae).

Previously described from only fragments of exoskeleton and juvenile specimens, the cave spider genus Troglodiplura (Araneae: Anamidae), endemic to the Nullarbor Plain, is the only troglomorphic member of the infraorder Mygalomorphae recorded from Australia. We investigated the distribution of Troglodiplura in South Australia, collecting and observing the first (intact) mature specimens, widening the number of caves it has been recorded in, and documenting threats to conservation. Phylogenetic analyses support the placement of Troglodiplura as an independent lineage within the subfamily Anaminae (the 'Troglodiplura group') and provide unequivocal evidence that populations from apparently isolated cave systems are conspecifics of T. beirutpakbarai Harvey & Rix, 2020, with extremely low or negligible inter-population mitochondrial divergences. This is intriguing evidence for recent or contemporary subterranean dispersal of these large, troglomorphic spiders. Observations of adults and juvenile spiders taken in the natural cave environment, and supported by observations in captivity, revealed the use of crevices within caves as shelters, but no evidence of silk use for burrow construction, contrasting with the typical burrowing behaviours seen in other Anamidae. We identify a range of threats posed to the species and to the fragile cave ecosystem, and provide recommendations for further research to better define the distribution of vulnerable taxa within caves and identify actions needed to protect them.