The Anomalodesmata Dall, 1899 includes some of the rarest and most specialised species of marine bivalves. This rarity has consequently constituted the greatest obstacle for understanding the internal relationships due to the low representativeness of species present in any phylogenetic reconstructions. Therefore, with the primary purpose of creating a more comprehensive morphological analysis, data including all the anomalodesmatan families were gathered into a cladistic analysis. Our data set includes, for the first-time, information about members of the families Clistoconchidae, Cetoconchidae, Protocuspidariidae, Spheniopsidae and the recently described Bentholyonsiidae. Information on shell morphology, anatomy and behaviour of anomalodesmatans was compiled through a review of the literature (from 1895 to 2022) and a re-analysis of shells and internal anatomy of some freshly collected and archived specimens in museum collections around the world. Our analysis suggests a deep division of the Anomalodesmata into two distinct clades: the first generally composed of shallow water species from 12 families and a second clade of a carnivorous lineage mainly comprising deep water species from 10 families. Consequently, a new topology for Anomalodesmata is suggested bringing new insights into the interfamilial relationships of this sometimes bizarre clade of bivalves.

The peculiar family Murrayidae, comprising the genera Murrayon, Dactylobiotus and Macroversum, contains relatively rare species living in hydrophilic and freshwater habitats on all continents, and contains two of the six exclusively freshwater tardigrade genera. This family probably represents an example of the evolution and persistence of an asexual lineage that differentiated into several taxa without sexual reproduction. Analyses of nuclear and mitochondrial genes (18S, 28S, ITS2 and cox1), and the increase of five taxa to the phylogenetic analyses of Murrayidae led us to infer that Murrayon is polyphyletic, being composed of two ‘species groups’ that also find morphological supports: the ‘dianeae group’ characterised by peculiar egg processes (rod-shaped and covered with a cuticular layer), animals with large, evident epicuticular pillars and small claws; and the ‘pullari group’ characterised by conical egg processes, animals with very small epicuticular pillars, and proportionally larger and longer claws. This latter group is a sister group to Dactylobiotus. Murrayon hastatus is the only species within the genus that has an uncertain position with eggs of the ‘dianeae group’ and animals of the ‘pullari group’. We propose the erection of Paramurrayon gen. nov. (for the ‘dianeae group’ of species), the emendation of Murrayon, and new taxonomic keys for both genera. Possible scenarios of the evolution of taxa within Murrayidae are hypothesised based on synapomorphic characters. Paramurrayon meieri sp. nov. from Norway is described with an integrative approach. Photographs of type material of Murrayon stellatus, Murrayon nocentiniae, Murrayon ovoglabellus and Macroversum mirum are shown for the first time, together with descriptions of new characters. Murrayon hibernicus is considered as nomen dubium and Murrayon hyperoncus is transferred to Macrobiotus pending further analyses.

The ant subfamily Leptanillinae (Hymenoptera: Formicidae) consists of minute soil-dwelling species, with several genera within this clade being based solely upon males, including Yavnella Kugler. The dissociation of males and workers has resulted in taxonomic confusion for the Leptanillinae. We here describe the worker caste of Yavnella, facilitated by maximum-likelihood and Bayesian inference from 473 partitioned ultra-conserved element loci, this dataset including 49 other leptanilline species, both described and undescribed. Yavnella laventa sp. nov. is described from seven worker specimens collected in south-western Iran from the Milieu Souterrain Superficiel, a subterranean microhabitat consisting of air-filled cavities among rock and soil fragments, which is subject to similar environmental conditions as caves. This species has bizarrely elongated appendages, which suggests that it is confined to cavities, in contrast with the soil-dwelling behaviour observed in other leptanilline ants. Based on its gracile phenotype relative to other Leptanillinae, Y. laventa shows remarkable adaptations for subterranean life, making it one of a very few examples of this syndrome among the ants. Moreover, the discovery of the worker caste of Yavnella expands our morphological knowledge of the leptanilline ants. We provide worker- and male-based diagnoses of Yavnella, along with a key to the genera of the Leptanillinae for which workers are known. The worker caste of Yavnella as known from this species is immediately recognisable, but the possibility must be noted that described workers of Leptanilla may in fact belong to Yavnella. Further molecular sampling is required to test this hypothesis.

Semisulcospira is a freshwater snail genus highly divergent in the ancient Lake Biwa, Japan, with a history of ~4 million years. Although the shell morphology, karyotype and molecular phylogeny of the genus have been well studied, the systematic status of several non-monophyletic species remains uncertain. In this study, we have evaluated the taxonomic accounts of the species previously identified as Semisulcospira decipiens, S. habei and relatives. We examined the genetic relationships using genome-wide SNP data and elucidated morphological variation among these using Random Forest classification. Morphological relationships between the name-bearing type of S. decipiens and the newly collected specimens were also evaluated. Morphological characteristics effectively discriminated between the nine genetic clusters, and the correlation among morphology and substrates was elucidated. We revised taxonomic accounts of S. decipiens, S. habei, S. arenicola, S. nakasekoae and S. ourensis and synonymised S. multigranosa, S. habei yamaguchi, S. dilatata under S. decipiens and S. fluvialis under S. nakasekoae. We also described two new species, Semisulcospira elongata sp. nov. and Semisulcospira cryptica sp. nov., and redefined two phylogroups of the lacustrine species as the Semisulcospira niponica-group and the Semisulcospira nakasekoae-group. Traits of the species examined exhibiting intraspecific variation in the different substrates and flow velocity may indicate the morphological and trophic adaptations. The habitat-related variation has certainly caused the taxonomic confusion of the lacustrine species. Lake drainage contributes to increasing the species diversity of the genus, generating ecological isolation between the riverine and lacustrine habitats.