Bathyvermilioides juliebrockae, Kupriyanova & Flaxman, 2024

Bathyvermilioides juliebrockae View in CoL n. sp.

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Fig. 5A–L View Figure 5

Material examined. Holotype: W.54380, Cocos (Keeling) Islands Territory , Investigator Ridge Abyssal (11°15'26"S, 97°58'08"E), depth 4980–4990 m, 12/10/2022 (not removed from the tube) GoogleMaps . Paratype: W.55302 (LK319), same as above (specimen removed for DNA, photos, and SEM) .

Description. Tube: white opaque, ostensibly free, with shiny surface, tusk-shaped, thick-walled, mostly quadrangular in cross-section, edges rounded and never denticulate ( Fig. 5A View Figure 5 ).

Radiolar crown: with 11 pairs of radioles in holotype, arranged pectinately, easily detachable from short radiolar lobes. Inter-radiolar membrane and stylodes absent. Terminal filaments of radioles thin, spirally twisted. Radiolar eyes and mouth palps not observed.

Peduncle: smooth, cylindrical, slightly thicker than remaining radioles, distal wings absent; inserted on left side between base of 1 st and 2 nd radioles.

Collar and thoracic membranes: collar covering bases of radiolar lobes, thin; four-lobed, with ventral lobe made of two lobes and distinctly higher than lateral ones ( Fig. 5B–D View Figure 5 ). Collar continuous with short rounded thoracic membranes ending at 2 nd chaetiger ( Fig. 5E View Figure 5 ).

Operculum: with soft membranous semi-transparent ampulla and distal part distinctly differentiated from basal part. Distally operculum covered with very hard, brownish semi-globular endplate with shiny surface ( Fig. 5F View Figure 5 ); conspicuous constriction between operculum and peduncle present ( Fig. 5F View Figure 5 ). Pseudoperculum absent.

Thorax: with 7 chaetigerous segments, 6 of which uncinigerous ( Fig. 5B–D View Figure 5 ). Small bundle of limbate collar chaetae. Subsequent chaetae limbate, of two sizes, Apomatus chaetae present ( Fig. 5G, H, e.g View Figure 5 ., the strongly bent chaeta). Uncini saw-shaped, with 9–10 teeth in profile view and pointed anterior fang ( Fig. 5J View Figure 5 ). Pair of prostomial eyes absent. Triangular depression absent ( Fig. 5C View Figure 5 ), thoracic tori widely separated and almost parallel to mid-lateral line of thorax.

Abdomen: paratype with 56 segments.Abdominal chaetae short, flat triangular with wide distal denticulate blade ( Fig. 5L View Figure 5 ). Long capillary chaetae absent in posterior chaetigers ( Fig. 5I View Figure 5 ). Uncini rasp-shaped with 9–10 teeth in profile and up to 5 rows of teeth above pointed anterior fang ( Fig. 5K View Figure 5 ). Achaetous anterior abdominal zone absent.

Size: total body length of paratype 13.8 mm, including 4.4 mm long radioles, 4.0 mm long thorax, 5.4 mm long abdomen, width of thorax 1.1 mm. Complete tube of holotype 22 mm long ( Fig. 5A View Figure 5 ). In holotype external tube diameter of tube mouth 1.5 mm, corresponding lumen diameter 1.1 mm.

Species diagnosis. The species is characterised by distinct quadrangular tusk-shaped tubes and the operculum covered with a very hard (questionably calcified) convex (semi-globular) brown endplate. This very hard endplate distinguishes the new species from other quadrangular-tubed taxa that have soft endplates. The diameter of the open posterior end suggests that the specimen originally settled on a small pebble or even a sand granule, and later broke free.

Distribution. Only known from seamounts off Cocos (Keeling) Islands, Indian Ocean, 4980–4990 m.

Etymology. The abyssal species is named in honour of Professor Julie Brock (University of Hawaii at Manoa, USA) for her numerous and important contributions to taxonomy of deep-sea serpulids.