Nicon salinus Hernández-Acántara & Dávila-Jiménez, sp. nov. Paratype (CNAP-ICML: POP-39-005). A Anterior region, ventral view; B Chaetiger 1; C Notopodium of chaetiger 1; D Chaetigers 2, 3; E Chaetiger 4; F Notopodium of chaetiger 8; G Chaetiger 9; H Chaetiger 16; I Posterior chaetiger. Abbreviations: ch3, ch2 = chaetigers 2 and 3; dC = dorsal cirrus; dLi = dorsal ligule; mLi = median ligule; pLo = postchaetal lobule; vC = ventral cirrus; vLi = ventral ligule. Scale bars: 200 μm (A), 50 μm (B, D–I), 20 μm (C).

Nicon salinus Hernández-Acántara & Dávila-Jiménez, sp. nov. Holotype (CNAP-POH-39-003). A Anterior region, dorsal view. Additional material (CNAP-PO-39-034/2027); B Chaetiger 10; C Chaetiger 30; D Chaetiger 50. Paratype (CNAP-ICML: POP-39-005); E Homogomph spiniger of chaetiger 1; F Homogomph articulation of spiniger of chaetiger 2; G Homogomph spiniger of chaetiger 10; H-K Homogomph falcigers of chaetigers 12, 15, 25, 30; L Pygidium, ventral view. Abbreviations: dC = dorsal cirrus; dLi = dorsal ligule; mLi = median ligule; pLo = postchaetal lobule; vC = ventral cirrus; vLi = ventral ligule. Scale bars: 200 μm (A), 50 μm (B–D), 10 μm (E, H, J, K), 5 μm (F, I), 20 μm (G), 100 μm (L).

Spinther bohnorum Tilic & Rouse, sp. nov., live and preserved specimens. A, B Live images of S. bohnorum sp. nov.; A Dorsal view, showing the notopodial fans covering the dorsum, the small prostomium (pro) and the bright orange colouration speckled with white spots; B Ventral view; C, D Holotype (S. bohnorum, SIO BIC A18597); C Dorsal view; D Ventral view, with long, protruded proboscis (pb) visible in all specimens and oocytes (oo) apparent in the holotype; E Paratype (S. bohnorum, SMF 32994), ventral view, also showing a protruded proboscis. Scale bars: 250 µm.

Spinther bohnorum Tilic & Rouse, sp. nov., holotype (SIO BIC A18597). (A–D) CLSM images showing autofluorescence. A Overview of dorsal and ventral views. The chaetigers are numbered with Roman numerals and the pygidial cirri (pc) are shown in the ventral view; B, C Notochaetae, with inset highlighting the bifid distal ends with spread tips; D Neuropodium, showing internal aciculae (ac), a single protruding falcate compound hook and oocytes (oo); E Light microscopy (LM) image showing the protruded proboscis and oocytes; F Close-up of a compound neuropodial hook, with the lateral tooth marked by an arrow; G Detailed view of the distal ends of both bifid and entire notochaetae. Scale bars: 250 µm (A, E), 100 µm (B), 50 µm (C, D), 25 µm (F, G).

Craspedochiton zefranki Vončina, sp. nov. A, B Holotype MNHN-IM-2019-34865, dorsal and ventral view, respectively; C, D Paratype SMF 380885, dorsal and ventral view, respectively. Scale bar: 5 mm.

Craspedochiton zefranki Vončina, sp. nov., holotype MNHN-IM-2019-34865. A, C, E Valves I, II, VIII, respectively, dorsal view; B, D, F Valves I, II, VIII, respectively, ventral view; G, H Valve I, VIII, respectively, lateral view. Scale bar: 250 μm.

Craspedochiton zefranki Vončina, sp. nov., holotype MNHN-IM-2019-34865. A, C, E Valve I, II, VIII; B, D Details of tegmental surface of valve II in the anterior and posterior part of lateropleural area, respectively; F Central portion of radula. Scale bars: 2 mm (A, C, E), 500 µm (B, D), 200 µm (F).

Craspedochiton zefranki Vončina, sp. nov., holotype MNHN-IM-2019-34865. A, B Dorsal girdle spicules from the anterior part of perinotum; C Dorsal girdle spicules and hair from the anterior part of perinotum; D Marginal spicules. Scale bars: (1) 200 µm (A), 100 µm (B), 300 µm (C, D).

Craspedochiton zefranki Vončina, sp. nov., holotype MNHN-IM-2019-34865. A–F Ventral spicules. A Spicules of the central part of hyponotum; B Spicules of the posterior part of hyponotum; C Single spicule from the anterior part of the mantle fold; D, E Spicules from the central part of the mantle fold; F Spicules from the posterior part of the mantle fold. Scale bars: 300 µm (A, B) 400 µm (C), 200 µm (D, E, F).

Ferreiraella charazata Sigwart, sp. nov. A Holotype SCSMBC240287, valves. From top to bottom: valve I, valve III (anterior view), valve V, valve VIII and valve VIII in lateral view; B Paratype 1 SMF 380825; C In situ photograph of multiple specimens (indicated with arrowheads) on sunken wood, together with other fauna. Scale bars: 2 mm.

Ferreiraella charazata Sigwart, sp. nov., holotype SCSMBC240287, SEM micrographs. A Aesthete pores, shown from valve I; B Radula; C Aesthete caps, shown from valve IV; D–F Girdle scales (perinotum). All scale bars: 100 μm (A, B, D–F), 25 μm (C).

Pycnodontochiton sinensis Sirenko, Zhang & Sigwart, sp. nov. A Holotype MBM229047, valves. From top to bottom: valve I (ventral view), valve I (dorsal view), valve III, valve VIII; SEM image on lower right: valve VIII in lateral view; B Paratype 1 MBM229048, lateral view; C Paratype 3 SCSMBC240288, Schwabe organ (dark region, adjacent to mouth). Scale bars: 2 mm (A, B), 0.25 mm (C).

Pycnodontochiton sinensis Sirenko, Zhang & Sigwart, sp. nov., SEM micrographs. A Paratype 2 SMF 380828, aesthete pores, shown from valve III; B–E Holotype MBM229047, radula (B), aesthete pores (C), girdle scales showing marginal scales (D), radula at a different position on the radular ribbon, showing the unusually large first uncinal (arrowheads; E); F, G Paratype 2 SMF 380828, ventral girdle scales (F), dorsal girdle scales (G). Scale bars: 100 μm (A, C, D, F, G), 500 μm (B, E).

Veleropilina gretchenae Sigwart & Steger, sp. nov., holotype SMF 373808. A Ventral view (line indicates approximate location of x-ray virtual cross section shown in image D); B Dorsal view; C Lateral view (right side); D Virtual cross section from synchrotron x-ray micro-CT, with arrowhead indicating position of radula; E Detail of teleoconch sculpture; F Apical cap, with arrowheads indicating the position of concentric ridges marking the transition to the reticulate teleoconch; G Detail of teleoconch sculpture showing minor irregularity. Scale bars: 1 mm (C–D), 100 μm (E–G).

Laevidentalium wiesei Sahlmann, 2012, type material. A–D Holotype HNC 43947, anterior (A), right side (B), posterior (C) and left side (D) views. Note the dry remains of the epizoic anemone attached to the anterior face of the shell; E–K Paratype HNC 82015, anterior (E), right side (F), posterior (G) and left side (H) views; dorsal aperture in lateral (I; scanning electron micrograph) and apical (J) view; scanning electron micrograph showing the microsculpture consisting exclusively of densely arranged incremental lines (K). Scale bars: 10 mm (A–H), 1 mm (I, K), 0.5 mm (J).

Laevidentalium wiesei Sahlmann, 2012, specimens from the AleutBio expedition. A–H Specimen SMF 366426, anterior (A), right side (B), posterior (C) and left side (D) views; close-ups of dorsal part of shell in posterior (E) and right side (F) view; detail of postero-ventral shell portion with growth mark indicated by arrowhead (G); micro-CT-based 3D reconstruction (left side view) and virtual cuts through the shell (perpendicular to the central axis) (H). Note the subcircular – wider than long – lumen of the ventral part of the shell that becomes circular dorsally; I–K Specimen SMF 373200 (shell broken during sampling event), right side (I) and posterior (J) views; close-up of the epizoic anemone attached to the anterior face of the shell (K); L Shell fragment from lot SMF 366427, scanning electron micrograph showing microsculpture. Scale bars: 10 mm (A–D, H – shell reconstruction, I–J), 5 mm (E–F, K), 2.5 mm (G), 2 mm (H – virtual shell sections), 1 mm (L).

Laevidentalium wiesei Sahlmann, 2012, anatomy and radula. A Specimen SMF 366426, virtual cross section from x-ray tomography with major internal structures indicated. Abbreviations: DV muscle, dorso-ventral muscle; B–G Specimen SMF 373200, virtual cross sections from x-ray tomography showing tests of ingested foraminifera (B–C; scaphopod soft body not shown for clarity), overview of radula (D; Abbreviations: cen, central tooth; lat, lateral tooth; mar, marginal tooth), close-up of lateral and marginal teeth (E), of central tooth (F) and detail of granulose face of the latter (G). Scale bars: 10 mm (A), 1 mm (B–C), 0.5 mm (D–E), 0.1 mm (F), 0.03 mm (G).

Myonera aleutiana Machado & Sigwart, sp. nov. shell and anatomy. A–C Photomicrography of holotype (SMF 373402), right and left valves plus a dorsal view, respectively; D–R Paratype (SMF 374320), right and left views, respectively; F–R Selected X-ray slices/images showing the arrangement and details of the pallial cavity organs and visceral mass; F–G Tomographic sagittal sections of different parts of the specimen; purple, yellow, red and green squares indicate the approximate areas of the transversal sections; H–R Tomographic transversal sections, from posterior to anterior orientation. Abbreviations: ap, anterior labial palp; aam, anterior adductor muscle; arm, anterior pedal retractor muscle; asm, anterior septal retractor muscle; b, bubble (artifact); bs, broken shell area; bt, byssal thread; ceg, cerebro-pleural (= circum-esophagic glanglia); css, crystalline style sac; dd, digestive diverticula; es, exhalant siphon; est, exhalant siphonal tentacles; f, foot; fl, foliaceus lamellae; gc, gastric caecum; gs, gastric shield; h + k, heart + kidney; hg, hind gut; hs?, haemocoel spaces; il, Inhalant lateral sinus; is, inhalant siphon; isc, infra-septal chamber; iss, inter-siphonal septum; ist, inhalant siphonal tentacles; lit, lithodesma; m, mouth; mm, mantle margin (ventral); o, oesophagus; ov, ovary; p, prey(s) inside stomach; pp, posterior labial palps; pu, pustules; pII, prodissoconch II; pam, posterior adductor muscle; prm, posterior pedal retractor muscle; r, rostrum; rr, radial ridge; rv, right valve; s, septum; sp, septal pores; sm, septal membrane; sr, secondary ridge; st, stomach; sph, sphincter of inhalant siphon; ssc, supra-septal chamber; ssh, siphonal sheath; u, umbones. Scale bars: 1.5 mm (A–C), 1 mm (D–R).

Myonera aleutiana Machado & Sigwart, sp. nov. comparison with other similar species from Atlantic and Pacific waters, including information on their occurrence, bathymetry, type numbers or original illustrations. External view of the shells of Myonera lamellifera, right view; M. limatula, right view; M. pailoloana, left view; M. alleni, right view (holotype not found); M. aleutiana sp. nov., right view; M. tasmanica, right view (see Knudsen (1970): figs. 110–111); M. sulcifera, right view; M. pretiosa, left view; M. atlasiana, right view (see Utrilla et al. (2020): fig. 6); M. kaiwa, left view (after Oliveira and Absalão (2009)); M. paucistriata, right view; M. lischkei, left view; Cuspidaria atlantica, right view; C. lamellosa, right and left views, respectively and Rengea murrayi, right view. Abbreviations: MNHN, Muséum national d'Histoire naturelle, France; MNCN, Museo Nacional de Ciencias Naturales, Spain; MCZ, Museum of Comparative Zoology, US; NHMD, Natural History Museum of Denmark; NHMUK, Natural History Museum, London, UK; NMW, National Museum Wales, UK; SMF, Senckenberg Museum of Frankfurt, Germany; USNM, Smithsonian National Museum of Natural History, US.

Apotectonia senckenbergae Momtazi & Riehl, sp. nov., macro-photograph of male holotype (SMF-62823). Scale bar: 2.5 mm.

Apotectonia senckenbergae Momtazi & Riehl, sp. nov., male holotype (SMF-62823) habitus (H), coxa 1-2 (C1, C2) and pereopods 1–2 (P1, P2). Scale bars: a = 2.5 mm, b = 0.5 mm.

Apotectonia senckenbergae Momtazi & Riehl, sp. nov., male holotype (SMF-62823) pereopods 4–7 (P4, P5, P6, P7), epimeral plates 1-3 (Ep 1-3) and urosomites 1-2 (Ur1-2). Scale bars: 0.5 mm.

Apotectonia senckenbergae Momtazi & Riehl, sp. nov., male holotype (SMF-62823) head appendages including left mandible (MdL), right mandible (MdR), first maxillae (Mx1), second maxillae (Mx2), maxilliped (Mxp), labium (Lbi), uropods 1–3 (U1, U2, U3), telson (T), antennae 1-2 (A1, A2). Scale bars: a = 1 mm, b = 0.5 mm.

Metharpinia hirsuta Souza-Filho & Andrade, sp. nov., female holotype (MOUFPE 22050). Habitus photograph. Scale bar: 1 mm.

Metharpinia hirsuta Souza-Filho & Andrade, sp. nov., female holotype (MOUFPE 22050). A Head lateral view; B Head dorsal view; C Antenna 1; D Antenna 2; E Left mandible; F Right mandible incisor; G Maxilla 1; H Maxilla 2; I Maxilliped. Scale bars: 0.3 mm (A–D), 0.1 mm (E–I).

Metharpinia hirsuta Souza-Filho & Andrade, sp. nov., female holotype (MOUFPE 22050). A Pereopod 1 (gnathopod 1); B Pereopod 2 (gnathopod 2); C Pereopod 3; D Pereopod 4; E Pereopod 5; F Pereopod 6; G Pereopod 7. Scale bars: 0.3 mm.

Metharpinia hirsuta Souza-Filho & Andrade, sp. nov., female holotype (MOUFPE 22050). A Epimeral plate 1; B Epimeral plate 2; C Epimeral plate 3; D Urosomite 3; E Uropod 1; F Uropod 2; G Uropod 3; H Telson. Scale bars: 0.3 mm (A–G), 0.1 mm (H).

Zeaione everta Boyko & Williams, gen. et sp. nov., adult female holotype (NMV J62877). A Habitus, dorsal view; B Right antennule, antenna and mouthparts, ventral view; C Barbula, dashed lines indicate third extension behind outer two extensions; D Left maxilliped with outer barbula lobe, external view. E Maxilliped spur, close-up showing setae. F Scales on outer barbula lobe; G Left oostegite 1, external view; H Left oostegite 1, internal view; I Dorsolateral view of pereomere 7 and pleomere 1 showing irregular protuberences and thalli of an unidentified species of Eccrinales (indicated by asterisk); J Pleon, ventral view; K Right pereopod 7; L Right pleopod 1; M Pleomere 6 showing biramous uropod on right side, scar of left uropod shown by asterisk. Abbreviations: A1 = antennule, A2 = antenna, Ex = exopod, En = endopod, Mo = mouthparts, per7 = pereomere 7, pleo1, 6 = pleomere 1, 6, Uro = uropod. Scale bars: 2 mm (A), 250 µm (B, D, G–I, K), 500 µm (C, L, M), 50 µm (E, F), 1 mm (J).

Zeaione everta Boyko & Williams, gen. et sp. nov., adult male paratype (allotype) (NMV J62877a). A Habitus, dorsal view; B Left antennule, antenna, mouthparts, maxillipeds (base shown by arrow) and pereopod 1, ventral view; C Left pereopod 7; D Pleon, ventral view. Abbreviations: A1 = antennule, A2 = antenna, Mo = mouthparts, P7 = pereopod 7. Scale bars: 250 mm (A, D), 50 mm (B, C).

Haploniscus bulbosus Henseler, Knauber & Riehl, sp. nov. macrophotographs. A, C, E male holotype (SMF 62946); B, D, F female paratype (SMF 62953). Scale bars: 1.8 mm.

Haploniscus bulbosus Henseler, Knauber & Riehl, sp. nov. male holotype (SMF 62946) habitus. A Lateral view; B Dorsal view; C Ventral view. Scale bars = 0.4 mm. Confocal laser-scanning micrographs with pseudo-colour.

Haploniscus bulbosus Henseler, Knauber & Riehl, sp. nov. male paratype (SMF 62947) habitus. A Dorsal view; B Ventral view; C Lateral view. Scale bars = 0.4 mm. Confocal laser-scanning micrographs with pseudo-colour.

Haploniscus bulbosus Henseler, Knauber & Riehl, sp. nov. dorsal habitus. A Male holotype (SMF 62946); B Female paratype (SMF 62953). Scale bar = 0.4 mm.

Haploniscus bulbosus Henseler, Knauber & Riehl, sp. nov. lateral habitus. A Male holotype (SMF 62946); B Female paratype (SMF 62953). Scale bar = 0.4 mm.

Haploniscus bulbosus Henseler, Knauber & Riehl, sp. nov. antennae of male holotype (SMF 62946; in situ) and female paratype (SMF 62953; in situ). A Male holotype antennula; B Male holotype antenna 2; C Female paratype antenna 2; D Female paratype antennula. Scale bars: 0.4 mm (A), 0.2 mm (B-D).

Haploniscus bulbosus Henseler, Knauber & Riehl, sp. nov. male paratype (SMF 62947) mouthparts. A Right maxilliped (dorsal); B Left maxilliped (dorsal; without epipod); C Left maxilliped (epipod); D Right mandible (ventral); E Left mandible (ventral); F Right maxilla; G Left maxilla. Scale bar = 0.15 mm. Confocal laser-scanning micrographs with pseudo-colour.

Haploniscus bulbosus Henseler Knauber & Riehl, sp. nov. male paratype (SMF 62947) pereopods. A Pereopod 2; B Pereopod 3; C Pereopod 4; D Pereopod 6; E Pereopod 1. Scale bar = 0.2 mm.

Haploniscus bulbosus Henseler, Knauber & Riehl, sp. nov. male paratype (SMF 62947) pleopods. A Pleopod 1; B Right pleopod 2; C Left pleopod 2; D Pleopod 3; E Pleopod 5. Scale bar = 0.15 mm. Confocal laser-scanning micrographs with pseudo-colour.

Haploniscus bulbosus Henseler, Knauber & Riehl, sp. nov. female paratype (SMF 62953) habitus. A Dorsal view; B Ventral view; C Lateral view. Scale bars = 0.4 mm. Confocal laser-scanning micrographs with pseudo-colour.

Macrostylis peteri Riehl, sp. nov., non-ovigerous female holotype (J60800) habitus. A Dorsal habitus; B Lateral habitus; C Pleotelson, ventral; D Pleotelson, posterolateral margin, statocyst and uropod; E Pleotelson uropodal insertion, ventral; F Sternites 1-3 with developing internal oostegites (ventral). Scale bars: 0.5 mm (A, B), 0.2 mm (C, D, F), 0.1 mm (E).

Macrostylis peteri Riehl, sp. nov., non-ovigerous female paratype (J46837) habitus. A Habitus, lateral; B Ventral outline, lateral; C Head with maxillipeds, ventral; D Habitus, dorsal; E Pleotelson, lateral. Scale bars: 0.5 mm (A, B, D), 0.2 mm (C, E).

Macrostylis peteri Riehl, sp. nov., non-ovigerous female paratype (J46837) habitus, lateral.

Macrostylis peteri Riehl, sp. nov., non-ovigerous female paratype (J46837) head appendages. A Head with antennula and antenna, lateral; B Maxilla; C Paragnaths (right side); D Antennula and antenna; E Maxillula with inner lobe separately illustrated (E1); F Maxilliped (ventral); G Maxilliped palp (frontal); H Maxilliped (dorsal). Scale bars: 0.2 mm (A, D), 0.1 mm (B, C, E-H).

Macrostylis peteri Riehl, sp. nov., non-ovigerous female paratype (J46837) mandibles. A Left mandible, dorsal (A1); incisor, ventromedial (A2); incisor, medial (A3); ventral (A4); B Right mandible, dorsal (B1); medial (B2); ventral (B3). Scale bar: 0.1 mm.

Macrostylis peteri Riehl, sp. nov., non-ovigerous female paratype (J46837) anterior pereopods. A Pereopod 1 (A1) with magnified dactylus (A2), with sensillae omitted (A3); B Pereopod 2; C Pereopod 3 (C1), with dactylus (C2) and ischium apical setae (C3) enlarged. Scale bar: 0.2 mm.

Macrostylis peteri Riehl, sp. nov., non-ovigerous female holotype (J60800) pereopods. A Pereopod 3 with magnified dactylus (A1); B Pereopod 4 with magnified propodus and dactylus; C Pereopod 5; D Pereopod 6; E Pereopod 7. Scale bar: 0.2 mm.

Macrostylis peteri Riehl, sp. nov., non-ovigerous female paratype (J46837) posterior pereopods. A Pereopod 4; B Pereopod 5; C Pereopod 6; D Pereopod 7. Scale bar: 0.2 mm.

Macrostylis cf. peteri Riehl, sp. nov., subadult male (J60803) habitus. A habitus dorsal; B Cephalothorax, left half, ventral; C Cephalothorax, lateral; D Pleotelson, lateral. Scale bar: 0.2 mm.

Macrostylis cf. peteri Riehl, sp. nov., subadult male (J60803) anterior pereopods. A Pereopod 1; B Pereopod 2; C Pereopod 3; D Pereopod 4. Scale bar: 0.2 mm.

Macrostylis cf. peteri Riehl, sp. nov., subadult male (J60803) posterior pereopods. A Pereopod 5; B Pereopod 6; C Pereopod 7. Scale bar: 0.2 mm.

Macrostylis cf. peteri Riehl, sp. nov., subadult male (J60803) pleopods. A Pleotelson, ventral (seventh pereopods omitted); B Pleopods 1 and 2, in situ; C Pleopod 1, distal part; D Pleopod 3; E Pleopod 4; F Pleopod 5. Scale bar: 0.1 mm.

Macrostylis peteri Riehl, sp. nov. type locality. Selected images from a camera tow (R/V SOUTHERN SURVEYOR cruise SS07 in 2005, transect T1, operation 25 in 700 m) showing deep-sea sediment, inhabited by unidentified megafauna species. Traces of life (Lebensspuren), such as burrows, pockmarks and faecal pellets indicate further megafaunal activity on and within the sediment. Images courtesy of Franzis Altjaus (CSIRO):

Hoplopolemius olo Jóźwiak & Stępień, sp. nov. Ovigerous female, holotype (SMF 57072), habitus. A Dorsal view; B Lateral view. Scale bar: 1 mm.

Hoplopolemius olo Jóźwiak & Stępień, sp. nov. Non-ovigerous female, paratype (SMF 57073). A Antennule; B Antenna; C Labrum; D Left mandible; D’ Molar of left mandible; D’’ Palp of left mandible; E Right mandible; E’ Molar of right mandible; F Maxillule endite; G Maxilla; H Labium; I Maxilliped; I’ Endite of maxilliped; J Epignath. Scale bars: 0.1 mm.

Hoplopolemius olo Jóźwiak & Stępień, sp. nov. Non-ovigerous female, paratype (SMF 57073). A Cheliped; B Pereopod 1; C Pereopod 2; D Pereopod 3; E Pereopod 4; F Pereopod 5; G Pereopod 6; H Pleopoda; I Uropoda. Scale bars: 0.1 mm.

Nesotanais thalassinus Stępień, sp. nov. Non-ovigerous female holotype [W60130], habitus. A Dorsal view; B Lateral view. Adult male allotype [W60131], habitus; C Lateral view. Scale bars: 1 mm.

Nesotanais thalassinus Stępień, sp. nov. Non-ovigerous female paratype [W60139] (A–B, F–K), male paratype [W60140] (C–D). A A1; B A2; C A1; D A2; E Lbr; F Left Md; G Right Md; G’ Molar of right Md; H Lbi; I Mx1 endite; I’ Mx1 palp; J Mx2; K Mxp. Scale bars: 0.1 mm.

Nesotanais thalassinus Stępień, sp. nov., non-ovigerous female paratype [W60139] (A, C–J), male paratype [W60140] (B). A Ch; B Ch; C P1; D P2; E P3; F P4; G P5; H P6; I Plp; J U. Scale bars: 0.1 mm.