Abyssocladia jeanvaceleti

Description: Growth form: The holotype consists of a pedunculated sponge, with a short stem and a vertically orientated disc shaped body with filaments radiating out in a single plane from the disc margin. (Figs. 6 A – C). The circular sponge bodies were 6 to 9 mm in diameter, and 0.4 to 0.6 mm thick. There were up to 50 filaments surrounding the body. The preserved filaments were 4.3 to 9.3 mm long and 0.1 mm in width, and highly contracted and or destroyed during collections, compared to the underwater images which show the filaments as up to one and a half times the width of the body (Figs. 6 A, B). The stem lengths were 14 to 22 mm long and 0.4 mm in width. All the specimens had spherical structures within the sponge body, which are most likely to be spermatocytes or oocytes. Some of the specimens such as G 338728 were still attached via a holdfast to the underlying rock strata. Colour: White in situ, on deck and in ethanol. Ectosomal skeleton: Thin membranous layer of the filaments is encrusted with small sigmancistras (Fig. 6 F). The sponge body and stem are encrusted isochelae overlaying the sigmancistras (Fig. 6 E). The lower stem and roots appear to be devoid of any specific ectosomal layer. Endosomal skeleton: The axis of the stem consists of longitudinally arranged styles. The main body and filaments consist of the radiating bundles of styles that form the filaments. The root axis consists of longitudinally arranged strongyles (Figs. 6 G, H). Megascleres: The sponge filaments are composed of two different but overlapping size groups of styles. The measurements of spicules for all the specimens are listed in Table 2, the spicule measurements for the holotype only are listed in the following text. The large mycalostyles present in the filaments are long and straight, with a blunt tip, they are 880 – (1120) – 1480 x 12 – (16) – 23 µm in size, with the slightest tylostyle thickening (Figs. 7 C, D). The smaller styles in the filaments (Figs. 7 E, F) are blunt styles, they are 360 – (520) – 703 x 5 – (8) – 12 µm in size. The stem is also composed of two different sizes of oxeote styles, the larger are long and straight, with a slight central thickening, and sharp points (Figs. 7 I, J), which are 1060 – (1240) – 1470 x 18 – (25) – 30 µm in size. The shorter oxeote styles of the stem have an obvious central thickening and a blunt tip (Figs. 7 G, H) and are 390 – (670) – 960 x 19 – (27) – 35 µm in size. The roots are composed of just one class of strongyle (Figs. 7 K, L) and are 320 – (480) – 680 x 8 – (11) – 26 µm in size. Microscleres: The microscleres are composed of a single size class of palmate isochelae (Fig. 7 A) 45 – (53) – 61 µm in size and a single size class of sigmancistras (Fig. 7 B) 8 – (11) – 13 µm in size.