Poecilosclerida Topsent, 1928

Order Poecilosclerida Topsent, 1928 View in CoL Family Phellodermidae van Soest & Hajdu, 2002 Genus Echinostylinos Topsent, 1927

D i a g n o s i s: A n a s t o m o s i n g b r a n c h e s, e r e c t bushes or semiglobular masses. Surface irregular or conulose. Skeleton of smaller ectosomal megascleres (styles or subtylostyles) or assuming a partly erect and partly tangential position and larger choanosomal styles forming an axially condensed mass or a vague reticulation of tracts and single spicules. Microscleres arcuate chelae and sigmas (modified from van Soest and Hajdu 2002).

Remarks: Diagnosis adapted to included styles as the smaller ectosomal megascleres.

Echinostylinos iatapiuna sp. nov. ( Fig. 2 View Fig ) urn:lsid:zoobank.org:act:838127E5-28EA-4812-AC34-F123F61D9A61

Material examined: Holotype. MNRJ 17631 View Materials , São Paulo ridge, Southwest Atlantic (Iata‒Piúna Expedition, ‘Shinkai’ submersible, Dive 156–1, YK13-04, st.02, -28.4033 / -40.9816), coll. H. Kitazato, depth 2300– 3300 m, 29.IV.2013. GoogleMaps

Diagnosis: Echinostylinos iatapiuna sp. nov. is the only Echinostylinos with a single category of megascleres (styles) and one category each of sigmas and spatulate arcuate tridentate isochelae larger than 60 µm.

Description: Cushion-shaped, roundish and flattened like a cookie, 30 × 2.7 mm in area, 7 mm thick. Compressible, with irregular surface, color beige in ethanol ( Fig. 2A View Fig ).

Skeleton: Ectosome and choanosome undifferentiated. Spongin abundant. Megascleres in unito paucispicular, inter-crossing, loose ascending tracts, further obscured by megascleres strewn in confusion. Sigmas scattered everywhere, and isochelae mainly in the ectosome ( Fig. 2B View Fig ).

Spicules: Megascleres a single category of styles ( Fig. 2C View Fig ), smooth, straight to slightly curved, tapering gradually to acerate ends, 1100–1219–1350 × 20–24.8– 28 µm. Microscleres isochelae and sigmas. Tridentate isochelae ( Fig. 2D View Fig ), with short, feebly developed spatulate teeth, 68–73.5–88 µm. Sigmas, smooth ( Fig. 2E View Fig ), C or S‒shaped, tapering gradually to both, asymmetrical apices, 60–71.1–88 µm.

Distribution and Ecology: Known only from its type locality, at bathyal depths (2300–3300 m) in the São Paulo ridge (SW Atlantic). The holotype was sampled associated to corals ( Solenosmilia spp. ).

Etymology: The specific epithet, iatapiuna , is proposed as a noun in apposition, and refers to the name of the oceanographic expedition in which this new species was collected.

Remarks: The species appearing closest to Echinostylinos iatapiuna sp. nov. is E. schmidtii ( Arnesen, 1903; type locality Norway, 500 m depth), sharing the same spicule categories, viz. one category each of styles, isochelae and sigmas. However, the dimensions of these are considerably different so that no doubt rests that both are separate valid species. The type of E. schmidtii is apparently lost (cf. Carvalho et al. 2016), but the original description of isochelae around 40, and sigmas around 20 µm long, sets it confidently apart from the new species’ 67‒88 µm long isochelae, and 60‒88 µm long sigmas. Additional species in Echinostylinos differ even further, both in terms of spicule categories present, as well as on morphometric aspects (see Table 2: a new version here of Table 8 in Carvalho et al. 2016). Comparison to the second new species proposed in the present study will be carried in the remarks to E. abyssalis sp. nov. (see below).

Echinostylinos abyssalis sp. nov. ( Fig. 3 View Fig ) urn:lsid:zoobank.org:act:E21D5BEE-CA32-4F83-BBF9-B09979F8D0ED

Material examined: Holotype. MNRJ 17633 View Materials , São Paulo Ridge, Southwest Atlantic (Iata‒Piúna Expedition, Shinkai submersible, Dive 1333, -28.5133 / -41.6533), coll. H. Kitazato, depth 4008 m, 23.IV.2013. GoogleMaps

Diagnosis: The only Echinostylinos with two categories of megascleres differentiated only by width, and microscleres, which are solely tridentate arcuate isochelae (tending to unguiferate morphology).

Description: Erect, perhaps semi-infundibuliform (half a funnel; but in situ image not very sharp, and collected specimens fragmented), fragile, largest fragment 75 mm long × 8 mm wide at the base, and 28 mm wide on apical region ( Fig. 3B View Fig ); smallest fragment 60 mm long × 4 mm wide at the base, and 29 mm wide on the apex. Compressible with irregular surface, color whitish in situ, beige in ethanol ( Fig. 3A View Fig ).

Skeleton: Ectosome with thinner megascleres (styles II) in ascending bundles. Choanosome with thicker megascleres (styles I) in ascending, loose, paucito multispicular tracts, sometimes forming ill-defined multispicular tracts. Microscleres abound all around ( Fig. 3B View Fig ).

Spicules: Megascleres are two categories of styles, both smooth and slightly curved, tapering gradually to acerate ends. Styles I, 572–781.8–854 × 17–19.7–24 µm ( Fig. 3C View Fig ); styles II, 446–497–582 × 7–10.6–12 µm ( Fig. 3D View Fig ). Microscleres, tridentate arcuate isochelae with pointy teeth, 29–32.5–36 µm ( Fig. 3E View Fig ).

Distribution and Ecology: Known only from its type locality, at an abyssal depth (4008 m) in the São Paulo ridge (SW Atlantic). Holotype founded growing on consolidated bottom.

Etymology: The specific epithet, abyssalis , is proposed as a noun in apposition, and refers to the type specimen’s depth zone of occurrence, the abyssal zone.

Remarks: Echinostylinos abyssalis sp. nov. is distinguished among its congeners as the sole species bearing two categories of styles (differentiated by width), and a single category of microscleres, namely tridentate, somewhat unguiferate, arcuate isochelae. When compared to other Echinostylinos spp. , E. brasiliensis (also from the SW Atlantic) appears the closest. However, E. brasiliensis presents only one category of megascleres and also of isochelae. With isochelae even smaller (22–28 µm) than those in the new species (29–36 µm). When compared to the other new species described above, E. abyssalis sp. nov. presents two categories of megascleres and only one of isochelae, while E. iatapiuna sp. nov. presents only one category of megascleres and isochelae plus sigmas. Regarding the isochelae shapes, E. abyssalis sp. nov. presents somewhat unguiferate alae, while in E. iatapiuna sp. nov. is spatulate. Additional species of Echinostylinos differ in terms of spicule categories present, and on morphometric aspects.