Plakortis insularis Moraes & Muricy, 2003 Figures 122 a–c Plakortis insularis Moraes & Muricy, 2003: 389, fig. 5; Moraes 2011: 68, several unnumbered figs. Material examined. RMNH Por. 9852, 9917, Suriname, ‘ Luymes O.C.P.S. II’ Guyana Shelf Expedition, station M97, 7.3083°N 54.1667°W, depth 130 m, bottom coarse sand, 16 April 1969; RMNH Por. 9870, Suriname, ‘ Snellius O.C.P.S. ’ Guyana Shelf Expedition, station F45, 6.4417°N 56.5467°W, depth 34 m, Van Veen grab, 7 May 1966. Description. (Fig. 122 a) Lobate masses with smooth surface. Size of largest specimen 7 x 3 x 3 cm. Color (in alcohol) orange-brown. Consistency firm, corky. Skeleton. At the surface there are rounded openings of 100–150 µm surrounded and subdivided into smaller openings by groups of perpendicular diods. Choanosome alveolar, with meshes of 30–40 µm diameter. Spicules. (Figs 122 b–c) Diods, triods. Diods (Figs 122 b), in a large size range, many are curved; they are possibly divisible in (1) larger 81–129 µm, and (2) smaller 11–28 µm spicules; overall sizes 11– 55 –129 x 0.5– 2.4 –6.5 µm. Triods (Figs 122 c), mostly equiactinal, actines 10– 31.9 – 38 x 1.5– 3.4 –4.5 µm (‘cladomes’ 22–61 µm). Distribution and ecology. Guyana Shelf, NE Brazil, 1–130 m depth (previously 1–12 m). Remarks. Of all the Plakortis simplex -like Central West Atlantic species, the specimens match closest with P. insularis. Using the key in Ereskovsky et al. (2014), likewise P. insularis comes out at the most likely match. The ectosome of my specimens is distinctly reticulate, which distinguishes it from P. edwardsi Ereskovsky, Lavrov & Willenz, 2014. The diods are very variable in size, but do not seem to be readily divisible in two distinct size categories such as found in P. dariae Ereskovsky, Lavrov & Willenz, 2014. From P. zyggompha (De Laubenfels, 1936) the present specimens differ in having larger diods (these are only up to 59 µm in the type of P. zyggompha). All these species are very similar and further research is necessary to establish whether they are all valid species.

Published as part of Van, Rob W. M., 2017, Sponges of the Guyana Shelf, pp. 1-225 in Zootaxa 1 on pages 193-194, DOI: 10.5281/zenodo.272951