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Molecular systematic studies of the anthozoan class Octocorallia have revealed widespread incongruence between phylogenetic relationships and taxonomic classification at all levels of the Linnean hierarchy. Among the soft coral taxa in order Malacalcyonacea, the family Alcyoniidae and its type genusAlcyoniumhave both been recognised to be highly polyphyletic. A recent family-level revision of Octocorallia established a number of new families for genera formerly considered to belong to Alcyoniidae, but revision ofAlcyoniumis not yet complete. Previous molecular studies have supported the placement ofAlcyonium verseveldti(Benayahu, 1982) in family Cladiellidae rather than Alcyoniidae, phylogenetically distinct from the other three genera in that family. Here we describe a new genus,Ofwegenumgen. nov.to accommodateO. verseveldticomb. nov.and three new species of that genus,O. coronalucissp. nov.,O. kloogisp. nov., andO. collisp. nov., bringing the total number of species in this genus to four.Ofwegenumgen. nov.is a rarely encountered genus so far known from only a few locations spanning the Indian and western Pacific Oceans. We present the morphological characters of each species and use molecular data from both DNA barcoding and target-enrichment of conserved elements to explore species boundaries and phylogenetic relationships within the genus. 

We document aggregations of an undescribed benthic solitary tunicate of the family Pyuridae from the Arabian Sea. This new genus was found forming dense thickets in shallow rocky substrates around Masirah Island and the Dhofar area in Oman. Such aggregations of tunicates have not been reported before from coral reefs in the Indo-West Pacific region and the Atlantic. This observation contributes to our understanding of the ecology and biogeography of ascidians, setting the stage for a comprehensive species description and in-depth analysis of this species. 

We document the benthic ctenophores Coeloplana sp. and Vallicula multiformis from Oman, extending their geographic range. A new Coeloplana species was found forming aggregations on gorgonians of two octocoral host genera, Melithaea and Euplexaura, representing associations previously unknown to occur in the Indo-West Pacific region. Our findings also illustrate the concurrent presence of the ectocommensal ophiuroid Ophiothela mirabilis, which adversely affects other Coeloplana species in the tropical West Atlantic, where it is considered invasive. This exploration contributes to our understanding of the biogeography, species distribution, and ectosymbiotic associations of these genera, setting the stage for a comprehensive species description and in-depth analysis of host relationships in future studies. 

Dense aggregations of serpulid worms were encountered in the Daymaniyat Islands (Gulf of Oman) from 10 to 20 m depth, over the period January–March, 2021. The species responsible for these aggregations belongs to the Filograna/Salmacina-complex (Annelida: Serpulidae). This species has been present in the area and observed along the Oman coastline, but high-density aggregates like this have not been reported before. The most probable cause of the aggregations, supported by field observations and Aqua-MODIS satellite data, was natural eutrophication with a subsequent algal bloom linked to the local winter monsoon. This observation emphasises the importance of documenting biodiversity and dynamics of reef communities along the Oman coastline. 

The type of the xeniid soft coral Sansibia flava (May, 1898) is re-described for the first time and its morphological diagnosis is presented. A subsequent integrated analysis of molecular and morphological characters of related Xeniidae, including species indigenous to the Indo-Pacific Ocean and invasive in the Atlantic (Brazil), led to the description of a new Sansibia species, as well as two new genera comprising an additional three new species. All of these taxa are encrusting, with polyps arising directly from a spreading basal membrane. Molecular phylogenetic analyses show that these genera are not sister taxa, thus further emphasizing the remarkable phylogenetic diversity of xeniids with such a growth form. The sclerites of all species are uniformly ellipsoid platelets, abundant throughout the colony. The species exhibit restricted, non-overlapping geographic ranges, with distinct genotypes (molecular operational taxonomic units) found in different marine realms. The results emphasize the importance of re-examination of original old type material while applying molecular phylogenetic analyses in order to delineate species boundaries and to recognize biodiversity patterns.