Although molecular data have proven indispensable in confidently resolving the phylogeny of many clades across the tree of life, these data may be inaccessible for certain taxa. The resolution of taxonomy in the ant subfamily Leptanillinae is made problematic by the absence of DNA sequence data for leptanilline taxa that are known only from male specimens, including the monotypic genus Phaulomyrma Wheeler & Wheeler. Focusing upon the considerable diversity of undescribed male leptanilline morphospecies, the phylogeny of 35 putative morphospecies sampled from across the Leptanillinae, plus an outgroup, is inferred from 11 nuclear loci and 41 discrete male morphological characters using a Bayesian total-evidence framework, with Phaulomyrma represented by morphological data only. Based upon the results of this analysis Phaulomyrma is synonymised with Leptanilla Emery, and male-based diagnoses for Leptanilla that are grounded in phylogeny are provided, under both broad and narrow circumscriptions of that genus. This demonstrates the potential utility of a total-evidence approach in inferring the phylogeny of rare extant taxa for which molecular data are unavailable and begins a long-overdue systematic revision of the Leptanillinae that is focused on male material.

The presence of cryptic species is fairly frequent in many invertebrate groups and even more so among invertebrates with simple morphology, such as nemerteans. Consequently, the use of molecular methods for species delimitation has become a needed tool to complement morphological analyses to better recognise such species. Nemertopsis bivittata is one example of species with subtle morphological variation, but ample geographic distribution, being a good candidate for a species complex study. Here we applied two mitochondrial genes, and 2903 single nucleotide polymorphism (SNP) variants in addition to morphological characters to investigate the presence of cryptic species among specimens previously identified as N. bivittata along the Brazilian Coast. To do so, specimens were collected at 15 different sites in the north-east, south-east and southern regions. Three new species of Nemertopsis are described based on morphological and molecular analyses: Nemertopsis caete sp. nov., Nemertopsis pamelaroeae sp. nov. and Nemertopsis berthalutzae sp. nov. The species N. pamelaroeae and N. berthalutzae present broad distributions from north-east to south-east; N. caete, however, is restricted to the north-east coast. This is the first study to use this combined approach in nemerteans and shows the advantages of integrating genomic markers with classical taxonomy, and applying objective approaches to delimiting species as independently evolving entities.

Thouarella Gray, 1870, is one of the most speciose genera among gorgonians of the family Primnoidae (Cnidaria : Octocorallia : Anthozoa), being remarkably diverse in the Antarctic and sub-Antarctic seafloor. However, their diversity in the Southern Ocean is likely underestimated. Phylogenetic analyses of mitochondrial and nuclear DNA markers were integrated with species delimitation approaches as well as morphological colonial and polyps features and skeletal SEM examinations to describe and illustrate three new species within Thouarella, from the Weddell Sea, Southern Ocean: T. amundseni sp. nov., T. dolichoespinosa sp. nov. and T. pseudoislai sp. nov. Our species delimitation results suggest, for the first time, the potential presence of Antarctic and sub-Antarctic cryptic species of primnoids, based on the likely presence of sibling species within T. undulata and T. crenelata. With the three new species here described, the global diversity of Thouarella has increased to 41 species, 15 of which are endemic to the Antarctic and sub-Antarctic waters. Consequently, our results provide new steps for uncovering the shelf benthonic macrofauna’s hidden diversity in the Southern Ocean. Finally, we recommend using an integrative taxonomic framework in this group of organisms and species delimitation approaches because the distinctions between some Thouarella species based only on a superficial examination of their macro- and micromorphological features is, in many cases, limited.

Taxonomic uncertainties and the lack of ecological knowledge can hinder the correct identification and the assignment of biogeographic status of marine species. The ascidian Asterocarpa humilis (Heller, 1878), originally described from New Zealand, has a broad distribution in shallow temperate areas of the Southern Hemisphere, having recently colonised areas of the Northern Hemisphere. A closely related species, Cnemidocarpa robinsoni Hartmeyer, 1916, has been reported in the South-Eastern Pacific and the South-Western Atlantic, and several authors considered it a junior synonym of A. humilis. We gathered for the first time morphological and genetic data from specimens from distant areas. We studied the morphology of specimens collected at seven locations of South America. We also re-examined specimens from museum collections and revised the available literature on these species. Genetic data were obtained from specimens from Argentina and compared with available sequences of A. humilis from Chile, New Zealand, England and France. Morphological and genetic analyses showed that all compared specimens were conspecific. Furthermore, specimens from different continents shared haplotypes and exhibited low genetic distance among them. These results, the biological characteristics of this ascidian, and its longstanding presence in different habitats from disjoint areas, allow us to question its native range. We support the idea that A. humilis is a cryptogenic and neocosmopolitan species that has been transported by maritime traffic through the Southern Hemisphere, revealing frequent processes of exchange through this wide area for more than a century, with presumably associated alterations in the marine biota.

Libinia, a genus of spider crabs, encompasses 10 valid species, three from the eastern Pacific and seven from the western Atlantic. Previous phylogenetic hypotheses based on molecular and larval morphological data suggested an uncertain position of the genus Libinia within the family Epialtidae. Therefore, we investigated the evolutionary relationships among the species of Libinia, and also suggested a position for this genus within the family. Phylogenetic trees were obtained from concatenated mtDNA sequences of 16S and COI fragments. Molecular dating methods were used to estimate the relative timing of origin and diversification within Libinia. Eighteen new primers were designed, and PCR conditions were standardised to amplify the COI fragments of older or poorly preserved pinned specimens, generating ∼550 base pair sequences. Phylogenetic hypotheses supported the monophyly of the genus. Species that occur in the eastern Pacific and the ones found in the western Atlantic do not form monophyletic clades related to this geographical separation. In the eastern Pacific, there is low phylogenetic proximity between Libinia mexicana and L. setosa; and since we did not sample L. peruana, we inferred that it should cluster with L. setosa or L. mexicana due to morphological similarity. Libinia spinosa is separate from the other species, L. mexicana was a sister group of L. cavirostris, and L. ferreirae was closely related to L. dubia and L. rhomboidea, which occur in the Gulf of Mexico and in the Caribbean, respectively. In the Gulf of Mexico, L. dubia and L. emarginata are closely related. Although L. erinacea was not sampled, we suggest, from previous studies, that it should group with L. dubia due to morphological similarities. The phylogenetic hypothesis suggests the monophyly of Libinia, with its origins at the late Eocene. Finally, the recovered clades based on two molecular markers agreed with a parallel, linked morphological study that is still in progress.

During a study of Discocyrtus Holmberg, 1878 and related genera, several species of alleged Pachylinae, mostly Discocyrtus, from southern Brazil were suspected of belonging in Roeweriinae. Herein, a maximum parsimony phylogenetic analysis of morphological characters was performed to test this hypothesis. Accordingly, the following taxonomic changes are herein proposed: the genus Bunopachylus Roewer, 1943 (currently in Pachylinae) is herein revalidated from synonymy with Discocyrtus, transferred to the Roeweriinae and now includes three species: B. armatissimus comb. nov. (for Discocyrtus armatissimus Roewer, 1913), B. orientalis comb. nov. (for Pachyloides orientalis Roewer, 1913) and B. occultus sp. nov. (which had been misidentified in the literature). A total of five new synonymies are proposed here: Discocyrtus milloti Roewer, 1943 = Discocyrtus coronatus Mello-Leitão, 1935 = Paradiscocyrtus trochanteralis Roewer, 1929 = Discocyrtus calcarifer Roewer, 1917 = Pachyloides orientalis Roewer, 1913, and Bunopachylus magnicalcar Roewer, 1943 (the type-species of Bunopachylus) = Discocyrtus armatissimus Roewer, 1913.