Bathyceramaster tasmanensis, Mah, 2025

Bathyceramaster tasmanensis View in CoL n. sp.

Figures 7A–E

Material Examined. Holotype. NMV F270799 About NMV . Central north 1000 Tasmanian seamounts, 44º 09' 11" S, 147º 11' 42" E, 999.8–1038.4 m, Coll.A.Williams, A.A. Weber and R-L. Erickson, RV Investigator , 27 November 2018. 1 wet spec. R = 4.9 r = 2.7. GoogleMaps

Paratypes. NMV F270801 About NMV . Central north 1000 Tasmanian seamounts, 44º 09' 11" S, 147º 11' 42" E, 999.8–1038.4 m, Coll. A. Williams, A.A. Weber and R-L. Erickson GoogleMaps , RV Investigator , 27 November 2018. 4 wet specs . R = 5.8 r = 3.3; R = 5.2 r = 3.1; R = 5.1 r = 3.0; R = 4.6 r = 2.4

Etymology. This species is named for the type collection locality in the Tasman Sea.

Diagnosis. Body weakly stellate to stellate, R/r = 1.67–1.9, arms triangular, broad at base, disk confluent with arms. Arm tips blunt. Interradial arcs weakly curved. Abactinal plates weakly tabulate, polygonal, the largest being hexagonal, surface flat covered by polygonal granules, 4 to 30, peripheral granules more rounded overall, but weakly angular in shape along radial regions, all widely spaced on each plate surface. No radial stellate radiating ossicles on abactinal plate bases. No pedicellariae. Marginal plates wide, 30–32 per interradius, pronounced forming 20% of distance “r”. Both series covered by granules, round, abundant but evenly spaced. Actinal plates with granules, 4 to 15 present on each plate surface, fasciolar grooves shallow but present. Furrow spines 5 to 6, mostly 6, blunt tipped, quadrate in cross section, in straight to palmate series. Subambulacral spines short, blunt, granular in two series of 3 to 4, all widely spaced.

Comments. Placement of this species was difficult owing its generalised appearance with observed characters suggesting placement in Mediaster and Ceramaster . It lacks the internal radiating abactinal plates diagnostic for Mediaster and Ceramaster , shows better developed fasciolar grooves, and shows better developed tabulae as defined herein. Complete granule cover present on the abactinal, marginal and actinal surfaces, but widespread granules are present in several goniasterid taxa. The disparity between deeper radial fasciolar grooves versus weakly developed to absent fasciolar grooves interradially was also observed as a diagnostic character for Bathyceramaster , suggesting placement pending further data.

Occurrence/Distribution. Tasmanian Seamounts, South Pacific, 999.8–1038.4 m

Description. Body weakly stellate to stellate, R/r = 1.67–1.9, arms triangular, broad at base, disk confluent with arms. Arm tips blunt. Interradial arcs weakly curved ( Fig. 7A, D).

Abactinal plates polygonal with more strongly hexagonal shaped plates present radially ( Fig. 7B). Plates smaller, densely arranged, more irregular interradially adjacent to superomarginal contact. Abactinal plate surface flattened, continuing to arm terminus. Plates covered by granules, 4 to 30, mostly 10–18, greater than 5 count along a 1.0 mm line. Peripheral granules, approximately 3 per side mostly round to polygonal, but rhomboid and narrow around radial regions. Fasciolar grooves present proximally and around radial regions, but more weakly developed to absent interradially. No radiating stellate ossicles on plate base. Superomarginal plates forming dorsal-facing boundary, approximately 20% of distance “r.” Madreporite quadrate in shape, flanked by four adjacent plates. No pedicellariae observed.

Superomarginal plates wide, 30–32 per interradius, widest interradially becoming more squarish distally along arms ( Fig. 7A, C). Marginal plate surface completely covered by coarse, round granules, approximately 50–90, evenly spaced. Inferomarginal plates with identical complete round granules. No pedicellariae.

Actinal region with 4 to 5 full series in chevron formation, but only adambulacral series extending along arm ( Fig. 7D, E). Plates round to irregularly polygonal in shape. Fasciolar grooves present, shallow. Plates covered by granules, 4 to 15, evenly spaced. Plates smaller, more irregular with fewer granules distally, at contact with inferomarginal plates.

Furrow spines 5 to 6, mostly 6, blunt tipped, quadrate in cross section, in straight to palmate series ( Fig. 7E, F). Subambulacral spines short, blunt, granular in two series of 3 to 4, all widely spaced. Oral plate furrow spines, 11 with a further spine (total of 2) projecting into mouth from each side. Spines are blunt, quadrate in cross-section. Five to six spines present on either side of central oral plate diastema ( Fig. 7E), further spines on oral plate decreasing in size, shape becoming more similar to those on remainder of actinal plate surface, widely spaced.