Sponges of the Guyana Shelf Author Van, Rob W. M. text Zootaxa 2017 1 1 225 journal article 37320 10.5281/zenodo.272951 e2c88f4c-3ac2-45f9-95e4-99b75561a081 1175-5326 272951 6D68A019-6F63-4AA4-A8B3-92D351F1F69B Hyalonema (Cyliconema) aff. conqueror Tabachnick, Menshenina, Lopes & Hajdu, 2009 Figures 123 a–k Hyalonema (Cyliconema) conqueror Tabachnick et al. , 2009 : 1244 , figs 1–2 (affinity). Material examined. RMNH Por. 9355, 9828, Guyana , ‘Luymes’ Guyana Shelf Expedition, station 80, 7.9333°N 57.2°W , depth 618 m , Van Veen grab, muddy bottom, 1 September 1970 . Description. ( Fig. 123 a) Small thin body tapering to an apical point, length 2 cm , diameter 0.5 cm . No atrial cavity. Tuft twice as long and almost as thick as the body, upper part of tuft provided with a few zoanthids. Skeleton. Predominantly consisting of diactins of various lengths and shapes, arranged lengthwise, with scattered (hypo-)dermal pentacins and hexactins. A few dermal pinular pentactins are present, but these are rare. Microscleres predominantly consisting of mesamphidiscs and micramphidiscs, few macramphidiscs, no micropentactins or microhexactins. Spicules. ( Figs 123 b–k) Diactins, hexactins, pentactins, pinular pentactins, macr-, mes- and micramphidiscs. Diactins ( Fig. 123 a) of the basal tuft at least 4 cm long, 180 µm thick. Diactins of the body ( Figs 123 b,b1), symmetrical, thinly tapering to sharp ends, with a vague centrotylote swelling, 1300– 2400 x 9–23 µm. Choanosomal asymmetrical diactins, usually curved, with opposed swollen and more tapering ends, with a centrotylote swelling, divisible in two distinct types, (1) entirely smooth, sometimes stylote ( Figs. 123 c,c1), 700– 1200 x 6–10 µm and (2) spined at both ends ( Figs 123 d,d1), 528– 1100 x 5–10 µm; overall asymmetrical diactins 528– 941 – 1200 x 5 – 7.7 –10 µm. Hypodermal pentactins ( Figs 123 e–f), in a large size range, with usually smooth, often slightly curved rays with lengths 174– 415 –760 x 5 – 17.3 –37 µm. Hypodermal hexactins ( Fig. 123 g), in a large size range, usually with smooth rays, but the smaller ones may have spined rays, with lengths 243– 544 –910 x 10 – 19.1 –38 µm. Dermal pinular pentactins ( Figs 123 h,h1), rare, pinular ray with longest spines halfway, ending in short spines, tangential rays lightly and sparingly spined, only a few were found in the slides (n=7), pinular rays 110–177 x 6–8 µm, tangential rays 54– 96 x 5–10 µm. Macramphidiscs ( Fig. 123 i), shaft provided with about 10–15 spined warts distributed evenly along it, teeth of umbel smooth-rimmed and slim, (n=8), length x width 145–305 x 60 –125 µm, length of umbels 60–100 µm. Mesamphidiscs ( Fig. 123 j), umbels together occupying ¾ of the length leaving only a short open shaft, umbels with densely arranged somewhat squarish teeth, shaft provided with spined warts which are often distributed rather irregularly, length 46– 66 –87 µm. Micramphidiscs ( Fig. 123 k), umbels with ‘flattened’ top, occupying 4/5 of of the length, shaft with several spines or high warts, length 15– 22 –31 µm. Distribution and ecology. Guyana Shelf, muddy bottom at 618 m . Remarks. No clearly matching descriptions were found for this hyalonematid. Using the key in Tabachnick & Menshenina (2002) the overall features appear closest to those of the subgenus Cyliconema (macramphidisc umbels wider than high, no sieve plates as in subgenus Coscinonema ). Apart from the intact (?) specimen RMNH Por. 9355, there is a basalia-only fragment RMNH Por. 9828 from the same station, assumed to be the same species. There is a certain similarity in spiculation with the Brazilian Hyalonema (Cyliconema) conqueror Tabachnick et al. , 2009 , but this has cup-shaped habitus, and possesses microhexactins and –pentactins, and pinular diactins, all lacking in the present specimen. Ornamented asymmetrical diactins such as found in the present specimen have not been reported in H. (C.) conqueror , unless these were considered ‘pinular diactins’. Similarly, there are similarities with Caribbean H. (Coscinonema) schmidti Schulze, 1899 and H. (Coscinonema) toxeres Schulze, 1887 , but these do not match the full set of characters. I refrain from erecting a new species for this material, because I suspect that dermalia have been damaged and I am not confident that the specimen has a complete spiculation. Possibly, this is a juvenile, damaged specimen of H. (C.) conqueror .