Barnacles of the genus Conopea are obligate epibionts of gorgonians and antipatharians. The species Conopea saotomensis Carrison-Stone et al. 2013, previously only known from the islands of São Tomé and Príncipe and the coast of Gabon, is reported from the Bijagós archipelago, Guinea-Bissau, based on morphological examination and DNA barcoding of specimens. The new record extends the known range of the species about 3000 km to the northwest.

Trilobites are an iconic group of extinct arthropods that lived in Palaeozoic oceans for c. 270 Ma, before their demise at the end of the Permian Period. Despite their considerable diversity (> 22 000 species) and abundance, particularly in Cambrian and Ordovician rocks, as well as intensive study for well over 200 years, trilobite systematics remains in a state of flux. In this contribution, the complex history of trilobite classification over the last century is briefly reviewed, including the seminal scheme published by Henry Swinnerton in 1915. The cryptogenesis problem, which relates to the supposedly obscure phylogenetic links between major post-Cambrian trilobite clades and their Cambrian sister taxa, is also discussed. Previous studies have suggested that the cryptogenesis problem is largely a taxonomic artefact, but the Cambrian origins of some post-Cambrian groups, such as the orders Proetida and Odontopleurida, are still unclear. Future directions for research on trilobite systematics are outlined, from taxonomic studies involving comprehensive documentation and extensive illustration of morphology at the species level, through to broad-scale phylogenetic analyses that initiate or test hypotheses about relationships across the major groups. Other ongoing issues to be addressed include identifying the sister group of Trilobita, and determining whether certain taxa, such as the suborder Agnostina and Cambrian family Burlingiidae, represent trilobites.

As the most diverse animal phylum, Arthropoda expectedly has a complex nomenclatural history. Fossil stem groups scattering diagnostic traits of extant clades further complicate the matter. There have been some recent attempts at reorganizing higher-level arthropod taxonomy based on new fossil interpretations and phylogenetic results. However, I argue that this proposed terminology has introduced unnecessary confusion both for semantic reasons and because the core of these interpretations is being falsified. In this paper, I defend the rightful use of Arthropoda and Euarthropoda as key terms in organizing the major branches of the arthropod evolutionary tree and emend Euarthropoda based on the most recent findings in this field. To help with the description of the tree when dealing with euarthropods that belong outside of the main radiative clade including extant taxa, I propose the name Cenocondyla nom. nov., which represents the least inclusive group containing both Mandibulata and Chelicerata.

The crustacean fauna of the Insect Bed (late Eocene), Isle of Wight is reviewed. The fauna comprises the branchiopod Branchipodites vectensis Woodward, 1879, ostracod Potamocypris brodiei Jones and Sherborn, 1889, and isopod Eosphaeroma margarum (Desmarest, 1822). In addition a new clam shrimp (Crustacea: Diplostraca: Spinicaudata) is described and named Paraleptestheria mitchelli sp. nov. This is the first record of the genus outside China and the first ‘conchostracan' to be described from the European Cenozoic.

Mitochondrial and nuclear sequence data from two Antarctic ameronothroid mites, Halozetes belgicae and Alaskozetes antarcticus, were used to address three key questions important for understanding both the evolution of biodiversity and its future conservation in the Antarctic Peninsula Region: i) Do populations of mites across the Antarctic Peninsula and Scotia Arc constitute distinct genetic lineages? ii) What implications does the spatial genetic structure in these species have for current understanding of the region’s glacial history? iii) What are the conservation implications of these findings? Our results indicate that both mite species have been present in the Antarctic since at least the Pliocene. At the regional scale, both species are comprised of a number of divergent, but sympatric, lineages that are genetically as distinct as some species within the genera Halozetes and Alaskozetes. At the local scale, complex structure suggests limited and stochastic post-Holocene dispersal. For both species, considerable spatial genetic structure exists across the region, similar to that found in other terrestrial invertebrates. These results support the implementation of stringent biosecurity measures for moving between the Scotia Arc islands and the Antarctic Peninsula, and throughout the latter, to conserve both evolutionary history and future evolutionary trajectories.

Metabarcoding, the coupling of DNA-based species identification and high-throughput sequencing, offers enormous promise for arthropod biodiversity studies but factors such as cost, speed and ease-of-use of bioinformatic pipelines, crucial for making the leapt from demonstration studies to a real-world application, have not yet been adequately addressed. Here, four published and one newly designed primer sets were tested across a diverse set of 80 arthropod species, representing 11 orders, to establish optimal protocols for Illumina-based metabarcoding of tropical Malaise trap samples. Two primer sets which showed the highest amplification success with individual specimen polymerase chain reaction (PCR, 98%) were used for bulk PCR and Illumina MiSeq sequencing. The sequencing outputs were subjected to both manual and simple metagenomics quality control and filtering pipelines. We obtained acceptable detection rates after bulk PCR and high-throughput sequencing (80–90% of input species) but analyses were complicated by putative heteroplasmic sequences and contamination. The manual pipeline produced similar or better outputs to the simple metagenomics pipeline (1.4 compared with 0.5 expected:unexpected Operational Taxonomic Units). Our study suggests that metabarcoding is slowly becoming as cheap, fast and easy as conventional DNA barcoding, and that Malaise trap metabarcoding may soon fulfill its potential, providing a thermometer for biodiversity.

Material previously referred to as Cassubia infercambriensis was re-examined and found to represent a composite fossil of a Peytoia-like anomalocaridid frontal appendage and an arthropod of uncertain affinities comparable to some bivalved arthropod taxa. The frontal appendage is referred to the genus Peytoia based on the presence of elongated ventral spines bearing a single row of auxiliary spines. As well as representing the oldest example of an anomalocaridid in the fossil record (Series 2, Stage 3), Peytoia infercambriensis is also the only record of this group from the East European Craton, therefore extending both the temporal and geographic range of the anomalocaridid family Hurdiidae.

The Guzhangian Weeks Formation preserves a diverse, yet virtually unstudied, non-trilobite arthropod fauna. Here we describe Tremaglaspis vanroyi sp. nov., the oldest representative of an enigmatic group of extinct arthropods, the Aglaspidida. Tremaglaspis was previously known from the Lower Ordovician and its morphology was regarded as particularly derived within the clade. Its occurrence in the Cambrian of Utah suggests that much of the early evolutionary history of the Aglaspidida remains unknown. A review of the environmental settings of previous aglaspidid findings suggests that these arthropods preferentially inhabited shallow-water environments, which may partially explain their limited fossil record.

A new sea spider (Arthropoda: Pycnogonida) from the Lower Devonian Hunsrück Slate (Germany) is described as Pentapantopus vogteli gen. et sp. nov. This is the fifth pycnogonid species known from this exceptional fossil Lagerstätte. The most conspicuous character of the new species is the presence of five pairs of walking legs. This character, in concert with a reduced abdomen, indicates a phylogenetic position of P. vogteli among the crown group pycnogonids. P. vogteli extends the knowledge of fossil pycnogonid body plans and underlines the significance of the Hunsrück Slate, as this locality shows the highest diversity of sea spiders for the entire fossil record so far.

Aglaspidids represent an obscure group of lower Palaeozoic arthropods with a patchy biogeographic distribution. Before the recent description of a representative from Tasmania, these arthropods were exclusively known from Laurentia during the late Cambrian. Here we describe a new species, Aglaspella sanduensis sp. nov., from the Furongian of China, confirming that aglaspidids sensu stricto were already widely distributed worldwide by the late Cambrian; this demonstrates that some aglaspidids had great dispersal capabilities. A new diagnosis of the genus Aglaspella is proposed and the species formerly known as Aglaspella eatoni is assigned to a new taxon, Hesselbonia gen. nov.

We examined mitochondrial DNA (COI) variability and distribution of Stereotydeus spp. in Victoria Land and the Transantarctic Mountains, and constructed Neighbour Joining (NJ) and Maximum Likelihood (ML) phylogenetic trees using all publicly available COI sequences for the three Stereotydeus species present (S. belli, S. mollis and S. shoupi). We also included new COI sequences from Miers, Marshall and Garwood valleys in southern Victoria Land (78°S), as well as from the Darwin (79°S) and Beardmore Glacier (83°S) regions. Both NJ and ML methods produced trees which were similar in topology differing only in the placement of the single available S. belli sequence from Cape Hallett (72°S) and a S. mollis haplotype from Miers Valley. Pairwise sequence divergences among species ranged from 9.5–18.1%. NJ and ML grouped S. shoupi from the Beardmore Glacier region as sister to those from the Darwin with pairwise divergences of 8%. These individuals formed a monophyletic clade with high bootstrap support basal to S. mollis and S. belli. Based on these new data, we suggest that the distributional range of S. shoupi extends northward to Darwin Glacier and that a barrier to dispersal for Stereotydeus, and possibly other arthropods, exists immediately to the north of this area.

The Late Carboniferous whip spider Graeophonus anglicus Pocock, 1911 (Arachnida: Amblypygi), is redescribed on the basis of the holotype and nine other specimens all preserved in sideritic nodules from the British Middle Coal Measures of Coseley, Staffordshire, UK. This species is clearly basal with respect to most living whip spiders, expressing numerous plesiomorphic character states and can be referred to both the suborder Paleoamblypygi and the ‘living fossil’ family Paracharontidae (with one Recent species), the latter based on an explict character of dorsal spination on the pedipalp femur. This suggests that crown-group Amblypygi originated by at least the mid-Palaeozoic.

Although levels of parasitism can vary greatly among individual bats of the same species, little is known about the characteristics of hosts that affect such variation. Bats were captured via mist nets from June 1995 to July 1997 from 28 localities throughout Paraguay. Over 17 500 ectoparasites were collected from 2909 bats; however, analyses of ectoparasite abundance were restricted to more abundant taxa of host and ectoparasite. We quantified the abundances of 29 taxa of ectoparasite on 19 species of bat host, as well as total abundance of ectoparasites regardless of taxonomic affiliation for 22 species of bat from Paraguay. The effects of host sex and host body size on these estimates of ectoparasite abundance were evaluated separately for each species of host. Ectoparasites did not respond consistently to host body size: ectoparasite abundance increased with host body size in 12 instances and decreased with host body size in 11 instances. Regardless of the existence or direction of effects of host body size on ectoparasite abundance, female hosts generally harboured more ectoparasites than did male hosts. Differences in host quality associated with the sex of bats, especially those related to behaviour, may be a more important determinant of ectoparasite abundance than are differences in size. Opportunities for host transfer are critical for species persistence of ectoparasites; consequently, ectoparasite populations on host individuals that form social groups or colonies should be larger, less prone to stochastic extinction, and have greater opportunity for speciation.

Limb morphology across the arthropods is reviewed using external morphological and internal anatomical data from both recent and fossil arthropods. Evolutionary trends in limb structure are identified primarily by reference to the more rigorous of the many existing phylogenetic schemes, but no major new phylogenetic inferences are presented. Tagmosis patterns are not considered, although the origins and patterns of heteronomy within the postantennulary limb series are analysed.

The phenomenon of annulation is examined and two basic types of annuli are recognised: terminal and intercalary. The annulation of the apical segment of a limb results in the formation of terminal flagella, and is typical of primarily sensory appendages such as insect and malacostracan antennules and maxillary palps of some hexapods. Intercalary annulation, arising by subdivision of existing subterminal segments, is common, particularly in the tarsal region of arthropodan walking limbs. Differentiating between segments and annuli is discussed and is recognised as a limiting factor in the interpretation of fossils, which usually lack information on intrinsic musculature, and in the construction of groundplans. Rare examples of secondary segmentation, where the criteria for distinguishing between segments and annuli fail, are also highlighted.

The basic crown-group arthropodan limb is identified as tripartite, comprising protopodite, telopodite and exopodite, and the basic segmentation patterns of each of these parts are hypothesised. Possible criteria are discussed that can be used for establishing the boundary between protopodite and telopodite in limbs that are uniramous through loss of the exopodite. The subdivision of the protopodite, which is typical of the postantennulary limbs of mandibulates, is examined. The difficulties resulting from the partial or complete failure of expression of articulations within the mandibulate protopodite and subsequent incorporation of partial protopodal segments into the body wall, are also discussed. The development and homology between the various exites, including gills, on the postantennulary limbs of arthropods are considered in some detail, and the question of the possible homology between crustacean gills and insect wings is critically addressed.

The hypothesis that there are only two basic limb types in arthropods, antennules and postantennulary limbs, is proposed and its apparent contradiction by the transformation of antennules into walking limbs by homeotic mutation is discussed with respect to the appropriate level of serial homology between these limbs.

A harvestman (Arachnida: Opiliones) is described from the Early Devonian (Pragian) Rhynie cherts, Aberdeenshire, Scotland. Eophalangium sheari gen. et sp. nov. is the oldest known harvestman. The material includes both males and a female preserving, respectively, a cuticle-lined penis and ovipositor within the opisthosoma. Both these structures are of essentially modern appearance. The Rhynie fossils also show tracheae which are, again, very similar to those of living harvestmen. This is the oldest unequivocal record of arachnid tracheal respiration and indicates that E. sheari was terrestrial. An annulate, setose ovipositor in the female suggests that it can be excluded from the clades Dyspnoi and Laniatores, in which the ovipositor lacks such annulations. However, the penis shows evidence of two muscles, a feature of uncertain polarity seen in modern Troguloidea (Dyspnoi). The presence of median eyes and long legs excludes Cyphophthalmi, and thus, E. sheari is tentatively referred to the suborder Eupnoi. Therefore, this remarkable material is implicitly a crown-group harvestman and is one of the oldest known crown-group chelicerates. It also suggests an extraordinary degree of morphological stasis within the eupnoid line, with the Devonian forms differing little in gross morphology – and perhaps in reproductive behaviour – from their modern counterp

The record of Ordovician Eurypterida from New York State, USA, is shown to be largely false. Twenty-nine species in 17 genera are here recognised as pseudofossils, reducing by more than 75% the total number of named Ordovician eurypterid taxa. Consequently, 10 families now have their first occurrence either later in the Ordovician or in the Early Silurian. The implications for eurypterid palaeoecology, diversity and evolution are not as straightforward as would be expected from such a drastic taxonomic revision. All Ordovician eurypterids are now known to occur in shallow-water, near-shore shales or fine-grained carbonates. Diversity measures indicate that the end-Ordovician extinction event appears to have had less effect on eurypterids than previously known, and their turnover is level in the Ordovician.

The first fossil opilioacariform mite (Acari: Opilioacariformes), Paracarus pristinus sp. n., is described from Baltic amber (Tertiary: Eocene). This well-preserved inclusion has six eyes and, thus, can be excluded from the derived, four-eyed genera. Based on characters such as the extremely long leg 4, it is assigned to the extant central Asian genus Paracarus Chamberlin & Mulaik, 1942. As with many Baltic amber inclusions, we lack an exact provenance for the type specimen, but the Baltic region is further north than the present day range of Recent opilioacariform species and suggests that the range of this group was once more extensive within Eurasia. The first solifuge (Solifugae) from Baltic amber is described as Palaeoblossia groehni gen. et sp. n. Based on its size and general appearance, it can be assigned to Daesiidae, and again represents an arachnid group which previously had a much wider geographical range. If adult, it may represent the smallest solifuge known.

Abundant arthropod trackways, assigned to Diplichnites gouldi, are described from the Lower Old Red Sandstone (Early Devonian; Lochkovian) of Pant-y-Maes quarry, Brecon Beacons, South Wales. The trackways are preserved on bedding planes of finely laminated planar and rippled siltstones. The sedimentology of the succession indicates that these units represent bar top and marginal deposits in a braided fluvial setting. Two trackway types are recognized (Type A and B); comparisons with contemporaneous myriapodous producers favour kampecarid and eoarthropleurid myriapods, respectively. Functional analysis of the trackways indicates that the producers were not using the most efficient, stable, walking techniques, but instead utilized in-phase ‘swimming stroke’-like gaits. Together with their occurrence on rippled surfaces, and lateral displacement of some trackways (attributed to currents), this indicates that they were produced sub-aqueously.

The first whipspider (Arachnida: Amblypygi) and three new examples of whipscorpions (Arachnida: Uropygi: Thelyphonida) are described from Lower Cretaceous (Aptian) strata of the Crato Formation, Ceará State, Brazil. The whipspider is described as Britopygus weygoldti gen. et sp. nov. It resembles members of the extant family Charinidae, but cannot be unequivocally placed. Two of the whipscorpions are referred to Mesoproctus rowlandi Dunlop, 1998 and one could be a subadult, since, like juveniles of extant species, it has a relatively broad anterior sternum. There are differences between these two specimens in pedipalp and flagellum morphology, but both characters are variable within extant species. The third and largest whipscorpion is incomplete and referred to Mesoproctus sp. Its carapace length is equal to or exceeds that of the largest known extant genus Mastigoproctus Pocock, 1894.

Microdecemplex rolfei, gen. and sp. nov., a new microarthropleuridean less than 5 mm long, is described from the Middle Devonian Panther Mountain Formation of New York State, U.S.A. The specimens consist of organically preserved cuticle, with some preserving the only cephalic structures known for arthropleurideans. A new order, Microdecemplicida, and a new family, Microdecemplicidae, are established. The probable phylogenetic position of the Microdecemplicida as one of the basal clades of Diplopoda is proposed.