Phloeocharinae is a small and likely non-monophyletic subfamily of rove beetles. The enigmatic genus Charhyphus Sharp, 1887 has long been placed in Phloeocharinae, whereas recent studies have found it to be phylogenetically very distant from the core members of this subfamily, suggesting the possibility that it actually deserves its own separate subfamily status. So far, the sole definitive fossil record for Charhyphus is known based on a single male from Eocene Baltic amber as represented by †Charhyphus balticus Shavrin, 2020. Here, we describe and illustrate another new Charhyphus species, †Charhyphus serratus sp. nov. Yamamoto & Shavrin, from Baltic amber based on a well-preserved female fossil. Considering the general proportions of the body and the head, this new species is most similar to †C. balticus. The new species differs from all known species by the development of strong serration of the lateral edges of the pronotum and features of the shape of the apical margin of the mesoventrite. By using X-ray micro-computed tomography, we succeeded in visualising not only the general habitus but also each individual body part, recovering a previously undocumented sclerite on the female internal genital segments in the genus. Morphological features of extinct and extant species of Charhyphus are briefly discussed. Figures of all extant Charhyphus species and a key for the genus are also provided. Our study is important for considering possible higher palaeodiversity, more common occurrence, and palaeobiogeography of Charhyphus.

Micromalthidae is a small relictual family of archostematan beetles that is well known for its unusual asexual reproductive system characterised by parthenogenetic, viviparous, larviform females and sterile adults. Here we describe the first micromalthid beetle from mid-Cretaceous Burmese amber (ca.100Ma). Protomalthus burmaticus gen. et sp. nov. differs from all presently known micromalthid beetles by the presence of distinct frontoclypeal, labroclypeal, and medicranial sutures. The finding represents the first Mesozoic record of an adult micromalthid beetle and confirms a Gondwanan distribution of the family during the Cretaceous. A list of micromalthid beetles is provided, together with a key to extant and fossil species.

This paper focuses on Antomicron, Leptolaimus and Procamacolaimus, three genera inhabiting coastal water systems of the Patagonian, Chubut and Santa Cruz provinces of Argentina, providing a review of their taxonomy for a new identification key. One new species belonging to the genus Antomicron and one new species belonging to the genus Leptolaimus of the family Leptolaimidae are described from Puerto San Julián, Santa Cruz province: Antomicron alveolatum sp. nov. has 35 alveoli and three precloacal supplements and Leptolaimus gabinoi sp. nov. is characterized by the structure and number of precloacal supplements (three) with hamate distal end with two hooks. Another species belonging to the genus Procamacolaimus of the family Camacolaimidae is described and recorded from Puerto Madryn, Chubut province of Argentina: Procamacolaimus dorylaimus.

This paper focuses on Diplolaimella and Diplolaimelloides two very cosmopolitan genera inhabiting lotic freshwater to salty water inland, groundwater and coastal waters systems, providing a review of their taxonomy with new keys, and their distribution on the east coast of Patagonia and inland Patagonia. Two new species belonging to the genus Diplolaimelloides of the family Monhysteridae are described from Patagonian salty lagoons and coastal areas, and the Chubut and Santa Cruz provinces of Argentina: Diplolaimelloides tehuelchus sp. nov. has four bursal and three postcloacal papillae, short gubernaculum, and spicules longer than 50 μm; it has been found in Patagonian salty lagoons and in high coastal salt marsh areas. Diplolaimelloides warwicki sp. nov. is characterized by the angular shape of the spicules and the long gubernaculum. Diplolaimella ocellata is recorded for the first time in Patagonian salty lagoons and new localities in coastal waters are recorded for Diplolaimella gerlachi Pastor de Ward, 1984.

The cosmopolitan and often ecologically dominant genus Terschellingia (Nematoda: Linhomoeidae), with 38 nominal species, is taxonomically a problematic taxon. Its species show high morphological plasticity, possess few diagnostic characters and identification keys are lacking. A revision of the genus was carried out based on morphological and morphometric data from the literature and from observations of specimens collected in Cienfuegos Bay, Caribbean Sea, Cuba. The diagnosis of the genus Terschellingia is emended. Of the current 38 nominal species, 15 are considered as valid species based on morphological characters related to size and position of amphidial fovea, presence/position of cephalic and cervical setae, presence/size/shape of pharyngeal bulb, shape of spicular apparatus and shape of tail. Tabular and pictorial keys were provided based on these characters. Three sympatric species: T. communis, T. gourbaultae and T. longicaudata were redescribed based on recently collected Cuban specimens. Each of them showed relatively large differences in body size in comparison with the respective type specimens, suggesting possible variation due to local environmental differences. The highest intraspecific variation pertains for the most widely spread cosmopolitan species T. longicaudata, suggesting that morphological plasticity enhanced adaptation to different environmental conditions. The notable taxonomic inflation within the genus (14 species inquirendae, 9 junior synonyms), probably also present in other highly specious genera of marine nematodes, can lead to an overestimation of the alpha-diversity.

The aim of this study is to analyse the Nephtyidae from the Gulf of California. Previous studies about the family Nephtyidae from the continental shelf of the Gulf include 21 species of which seven have been synonymized by several authors, so that at present only 14 species are recognized. In this study, 1763 specimens of Nephtyidae from the continental shelf of the Gulf of California were examined. Eight species were identified, from which Aglaophamus longicirrata sp. nov. and Aglaophamus foliosa sp. nov. are newly described. Aglaophamus longicirrata sp. nov. is characterized by the presence of very long dorsal cirri in median parapodia and by having 16 rows of subterminal papillae with 3–7 papillae per row, and a pair of middorsal papillae on the proboscis. Aglaophamus foliosa sp. nov. is characterized by foliaceous long dorsal cirri; the proboscis bears 16 rows of subterminal papillae and an irregular number of papillae per row, from 5 to 15. A taxonomic key is presented for the species of Nephtyidae recorded from the continental shelf of the Gulf of California, including the two new species of Aglaophamus.

The new genus Vahliella is recognized as a genus since molecular studies have shown that the subgenus Micropannaria of Fuscopannaria differs so much from this genus that it cannot even be placed in the Pannariaceae. While its family position remains unclear, it is certainly best established as a genus, as it is recognizable also on morphological and chemical characters. Unlike the mainly warm-temperate genus Fuscopannaria, it is restricted to cold-temperate regions. Presently it is known to contain eight species, a key to which is given. The following new combinations are introduced: Vahliella adnata (P. M. Jørg. & Upreti), Vahliella atlantica (P. M. Jørg. & P. W. James), Vahliella californica (Tuck.), Vahliella globuligera (Fryday & P. M. Jørg.), Vahliella hookerioides (P. M. Jørg.), Vahliella labrata (P. M. Jørg.), Vahliella leucophaea (Vahl), Vahliella saubinetii (Mont.).

Several type series of unusual and poorly known genera of Syllidae have been examined. New diagnoses for the following genera and re-descriptions of their type species are provided: Anguillosyllis, Clavisyllis, Lamellisyllis and Nuchalosyllis; Brachysyllis, previously synonymized with Dioplosyllis, is herein considered to be a valid taxon. The species Brachysyllis infuscata is also re-described. Three genera are considered to be non-valid taxa: Braniella, synonymous with Anguillosyllis; Alluaudella, synonymous with Odontosyllis; and Exogonella, synonymous with Parexogone. Their type species herein are re-described and assigned to their corresponding valid genus. Finally, Exogonoides is considered nomina dubia since its relationships with other syllids could not be established. Keys to species of Anguillosyllis and Brachysyllis are also included.

Three new species of Lepraria, L. celata, L. humida, and L. sylvicola, are described from Europe. They each possess a finely granular unstratified thallus containing fatty acids and atranorin, but can be distinguished from each other by the type of fatty acids present and by their ecology. Anthraquinones are present in subthalline hyphae of L. humida and L. sylvicola, and are also reported for L. atlantica. Toensbergianic acid can be produced by L. jackii as a minor compound. A key is presented to species of Lepraria containing fatty acids and atranorin as major substances.