This study investigates the molluscan fauna of the South Azorean seamount chain (SASC), which comprises several seamounts culminating in 300-1600 m depth, separated by distances less than 200 km. Material was collected mainly by dredging and comprises mostly empty shells. A total of over 111 000 shells representing at least 439 species (409 identified) was collected. Larval development was inferred from protoconch morphology and the assemblage comprises species with planktotrophic larvae, with non-feeding planktonic larva and with lecithotrophic larvae with direct development. The direct developers are more prevalent among species endemic to the SASC in the upper bathyal part (300-800 m) of the seamounts, whereas most planktotrophic species are shared with the Lusitanian seamounts and/or the European mainland. Nevertheless, there are notable exceptions to this trend, where species with non-planktotrophic larvae are also widespread, and a large proportion of the species with non-feeding planktonic larvae are shared with Eastern and/or Western Atlantic. Level of endemism of Mollusca is high within the SASC (22.5% overall, 35.8% considering only the interval < 800 m) and even higher (32.6% overall) when considering together the SASC and the Azores. The generic composition and large set of overlapping fauna suggests a strong relation to the temperate Eastern Atlantic, whereas only 19% of the species are shared with the Western Atlantic. The occurrences of the species in each sampling location are detailed in supplementary Table S1, the list of species with their attributes is given in Table S2, and the list of species with their score in other areas of the Atlantic Ocean Table S3.

This study investigates the molluscan fauna of the South Azorean seamount chain (SASC), which comprises several seamounts culminating in 300-1600 m depth, separated by distances less than 200 km. Material was collected mainly by dredging and comprises mostly empty shells. A total of over 111 000 shells representing at least 439 species (409 identified) was collected. Larval development was inferred from protoconch morphology and the assemblage comprises species with planktotrophic larvae, with non-feeding planktonic larva and with lecithotrophic larvae with direct development. The direct developers are more prevalent among species endemic to the SASC in the upper bathyal part (300-800 m) of the seamounts, whereas most planktotrophic species are shared with the Lusitanian seamounts and/or the European mainland. Nevertheless, there are notable exceptions to this trend, where species with non-planktotrophic larvae are also widespread, and a large proportion of the species with non-feeding planktonic larvae are shared with Eastern and/or Western Atlantic. Level of endemism of Mollusca is high within the SASC (22.5% overall, 35.8% considering only the interval < 800 m) and even higher (32.6% overall) when considering together the SASC and the Azores. The generic composition and large set of overlapping fauna suggests a strong relation to the temperate Eastern Atlantic, whereas only 19% of the species are shared with the Western Atlantic. The occurrences of the species in each sampling location are detailed in supplementary Table S1, the list of species with their attributes is given in Table S2, and the list of species with their score in other areas of the Atlantic Ocean Table S3.

Skeletal colony fragments of the deep-water coral Desmophyllum pertusum were digitized using the 3D surface scanner Artec Space Spider with the software Artec Studio 15. Multiple individual scans of each specimen were assembled through Auto-alignment, and converted into watertight polygonal 3D models (resolution 0.2 mm) using Sharp fusion. Noise and artefacts were removed whenever necessary with the Small-object filter, Eraser and Defeature brush tools. Convex hulls of the 3D models, as well as geometric (volume and surface area) measures of 3D models and convex hulls were computed in MeshLab v2020.12. Compactness was calculated as the ratio of mesh volume to convex hull volume. Packing was calculated as the ratio of mesh surface area to convex hull surface area. Compactness and packing are both dimensionless variables.

Skeletal colony fragments of the deep-water coral Desmophyllum pertusum were digitized using the 3D surface scanner Artec Space Spider with the software Artec Studio 15. Multiple individual scans of each specimen were assembled through Auto-alignment, and converted into watertight polygonal 3D models (resolution 0.2 mm) using Sharp fusion. Noise and artefacts were removed whenever necessary with the Small-object filter, Eraser and Defeature brush tools. Convex hulls of the 3D models, as well as geometric (volume and surface area) measures of 3D models and convex hulls were computed in MeshLab v2020.12. Compactness was calculated as the ratio of mesh volume to convex hull volume. Packing was calculated as the ratio of mesh surface area to convex hull surface area. Compactness and packing are both dimensionless variables.

This dataset shows of the global distribution of cold-water corals. Occurrence records are given for the subclass Octocorallia (octocorals; also known as Alcyonaria) and four Orders (in Class Anthozoa): Scleractinia (reef-forming corals), Antipatharia (black corals), Zoanthidae (encrusting or button polyps), and Pennatulacea (sea pens). Occurrence records are also available for the order sub-Order Filifera (lace corals) in Class Hydrozoa.