Next-generation sequencing has helped phylogenetic resolution across the tree of life, but molecular data may be inaccessible for rare extant taxa. Here, the phylogeny of the ant subfamily Leptanillinae (Hymenoptera: Formicidae) is jointly inferred from 11 nuclear loci and male morphology. This methodology resolves the affinity of the enigmatic genus Phaulomyrma, which is known only from males and has not been sequenced. Therefore, this study demonstrates the utility of a total-evidence approach in resolving the phylogeny of extant organisms for which molecular data are difficult to acquire.

Nemertopsis bivittata is a nemertean with subtle morphological variation resulting in an unsettled taxonomic history.We use morphology, two mitochondrial genes and Single Nucleotide Polymorphism (SNPs) markers to investigate this complex in Brazil, revealing that it comprises three species. The species N. pamelaroeae and N. berthalutzae present broad distribution from north-east to south-east; N. caete, however, is restricted to the north-east coast. This study shows the advantages of integrating genomic markers with classical taxonomy to better resolve intricate species complexes.

The family Primnoidae includes common and diverse gorgonian lineages in the Antarctic benthic communities, where they play an essential role in structuring these habitats. However, taxonomic identifications of primnoids to the species level can be challenging. The complementary use of molecular and morphological data of dozens of primnoid colonies recovered from the Weddell Sea has allowed us to recognise new species within the primnoid genus Thouarella, providing further steps to uncover the shelf benthonic macrofauna’s hidden diversity in the Southern Ocean.

Morphological and genetic analyses in specimens of two similar ascidians from different worldwide areas, particularly from SW Atlantic, revealed that they belong to a single species: Asterocarpa humilis. Longstanding presence in natural and artificial habitats along disjoint areas of the Southern Hemisphere suggests its human transport and its neocosmopolitanism. We propose a cryptogenic status for this species in the Southern Hemisphere.

Libinia is a genus of spider crabs, a diverse group in form, size, and habitat. This genus is amphi-American and encompasses 10 species with diversification at the late Eocene. Some species share morphological traits, habits, and distribution, which led us to investigate them. We present a molecular phylogenetic hypothesis of Libinia based on molecular characters. We found that Libinia is monophyletic and that it originated before the closure of the Isthmus of Panama.

There are many gaps in our understanding of the Neotropical opilionid fauna. As one of the most diverse genera of Gonyleptidae, Discocyrtus (as known nowadays) has many synonyms and incorrect geographical records. Here, we explore two species of Discocyrtus and reveal five new synonyms and a new species (hidden for almost 70 years in the literature). That species group is transferred to Bunopachylus (a genus restored from synonymy with Discocyrtus) and shows affinities with Roeweriinae.