Plakortis petrupaulensis sp. nov. (Fig. 2) Specimens examined (4). Holotype: MNRJ 11828, Enseada, São Pedro e São Paulo Archipelago, Brazil, on overhang, 4 m depth; Fernando Moraes coll., 15 September 2007. Paratypes: MNRJ 11817, 25 September 2007, 13 m depth; MNRJ 11826, 21 September 2007, 5 m depth; MNRJ 11839, 15 September 2007, 4 m depth; all from São Pedro e São Paulo Archipelago, Brazil; Fernando Moraes coll. Specimens examined for comparison. P. angulospiculatus: UFRJPOR 3900, 4791, Fernando de Noronha Archipelago, Brazil. UFRJPOR 4032, Tamandaré, Pernambuco State, Brazil. UFRJPOR 4116, 4118, Carrie Bow Key, Belize. Plakortis hooperi Muricy, 2011: QMG 312880, Papua New Guinea. Plakortis insularis: UFRJPOR 3917, 4803; MNRJ 2126, 2138; all from Fernando de Noronha Archipelago, Brazil. Plakortis microrhabdifera: MNRJ 2165, 2170, 2940, all from Atol das Rocas, Brazil. Plakortis potiguarensis sp. nov.: UFPEPOR 585, Urca do Tubarão, Potiguar Basin, Rio Grande do Norte State, Brazil. Plakortis spinalis sp. nov.: MNRJ 8597, Sapata Cave, Fernando de Noronha Archipelago, Brazil. Diagnosis. Plakortis thinly encrusting, light brown in vivo, with a tangential ectosomal skeleton disorganized or vaguely reticulate, and a disorganized choanosomal skeleton. Both ectosomal and subectosomal lacunae are absent. Spicules are smooth diods and tuberculate microrhabds, together with siliceous spheres; triods are absent. Description. Shape thinly encrusting, up to 4.5 by 3.0 cm wide and 0.5 cm thick (Fig. 2 A, B). Color in vivo light brown with dark patches and light brown to yellowish-cream internally; it becomes all light brown or grayishcream in alcohol. Surface smooth but irregular, uneven. Oscules circular or elliptical, 1–3 mm in diameter, with a slightly elevated rim in vivo and contracted in preserved specimens. Consistency firm, cartilaginous to compressible. Skeleton. Tangential ectosomal skeleton disorganized, but vaguely reticulated in parts of some specimens (Fig. 2 C). Both ectosomal and subectosomal lacunae are absent. Ectosome and choanosome undifferentiated. Choanosomal skeleton disorganized, with few traces of reticulation (Fig. 2 D). Spicules. Diods thin, sinuous, smooth, with rounded or sharp ends. The central bent varies from slightly to strongly marked, some very irregular (Fig. 2 E): 28-55-76 / 1-1.9-3 µm (n=80). Microrhabds slightly sinuous, irregular, and typically tuberculate (Fig. 2 F): 1-6.2-18 / 0.5-2.4-3.0 µm (n=80). Spheres smooth, ovoid and flattened are common (Fig. 2 F): 1-6.2-35 µm in diameter (n=80). Triods absent. Habitat and ecology. Specimens were collected between 4 and 13 m depth on vertical walls, always on hard substrate. Small calcareous sponges were observed growing on their surface. Distribution. Endemic from São Pedro e São Paulo Archipelago, NE Brazil (Fig. 1). Taxonomic remarks. Plakortis petrupaulensis sp. nov. belongs to the group of Plakortis with microrhabds, which also includes P. microrhabdifera, P. lita de Laubenfels 1954, P. hooperi Muricy 2011 and P. m y r a e Ereskovsky, Lavrov & Willenz 2013. The new species is mostly similar to P. microrhabdifera in the brown color, smooth surface, disorganized choanosomal skeleton and absence of triods. They differ by the larger size of diods (50–101 µm long), a double tangential ectosomal reticulation, and the presence of non-tuberculate microrhabds in P. microrhabdifera (cf. Moraes & Muricy 2003). Plakortis hooperi is distinguished by a lighter color, presence of subectosomal lacunae and triods, larger diod size (79–148 µm) and absence of tubercles in microrhabds (Muricy 2011). Plakortis lita differs from P. petrupaulensis sp. nov. by its dark color (dark brown or black), slimy surface, reticulate tangential ectosomal skeleton, non-tuberculate microrhabds, and presence of triods (de Laubenfels 1954; Muricy 2011). Plakortis myrae differs from the new species by the presence of triods, larger diods (66–119 µm) and smooth microrhabds. The new species differs from all other species of Plakortis by the presence of tuberculate microrhabds. Etymology. The name petrupaulensis refers to the type locality of the species, São Pedro e São Paulo Archipelago, in NE Brazil.

Published as part of Domingos, Celso, Moraes, Fernando & Muricy, Guilherme, 2013, Four new species of Plakinidae (Porifera: Homoscleromorpha) from Brazil, pp. 530-544 in Zootaxa 3718 (6) on page 533, DOI: 10.11646/zootaxa.3718.6.2, http://zenodo.org/record/218896