Eurypon oxychaetum sp. nov. (Figures 1–3, Table 1)

Type locality: Brazil, Paraíba State.

Type specimens: Holotype. UFPEPOR 3007, off Conde Municipality (07° 21' S – 034° 38' W), Paraíba State, Brazil, depth 30 m, st. 20, Algas Project (01/VII/1969) . Paratype. UFPEPOR 3023 and UFPEPOR 3026, off Pitimbu Municipality (07° 30' S – 034° 45' W), Paraíba State, Brazil, depth 10 m, st. 28, Algas Project (06/X/1969) .

Diagnosis. Eurypon with large subtylostyles (1025–2125 / 13–39 µm), subectosomal styles (283–412 / 2–5 µm), two categories of acanthostyles (I = 290–650 / 13–26; II = 68–135 / 3–6 µm, length / width) and oxychaetes (77–119 µm).

External morphology (Fig. 2A–B). Thinly encrusting sponge, 0.5–1.0 mm thick. Projecting spicules through surface. Consistency is fragile. Oscula were not found. Colour is beige (preserved in ethanol 80 %), colour in vivo unknown.

Skeleton (Fig. 2C). No special ectosomal skeleton. Choanosomal skeletal arrangement microcionid. Dense basal layer echinated by subtylostyles and acanthostyles protruding through surface. Styles and oxychaetes dispersed in the subectosomal region.

Spicules (Fig. 3A–J). Choanosomal subtylostyles, occasionally tylostyles (1025– 1727.5 –2125 / 13– 24.4 –39 µm): long, thin, smooth, curved and blunt tips (Fig. 3A–B); Subectosomal styles (283– 354.5 –412 / 2– 3.2 –5): thin, smooth and curved (Fig. 3C–D); Acanthostyles I (290– 426.5 –650 / 13– 19.6 –26 µm): robust, slightly curved, and with few curved spines over the shaft directed to the base (Fig. 3G–H); Acanthostyles II (68– 97.9 –135 / 3– 4.9 –6 µm): small, thin, straight to slightly curved, abundant curved spines directed to the base (Fig. 3I –J); Oxychaetes (77– 100.8 –119): small, straight and with of spines over the whole shaft (Fig. 3E–F).

Distribution and ecology (Fig. 1). Brazil: Northeastern Region: Paraíba State, between 10– 30 m. Found on calcareous algae during a historical expedition at Paraíba State in 1969.

Etymology. The specific epithet oxychaetum refers to the presence of oxychaete spicules, exclusive of the new species.

Remarks. Eurypon oxychaetum sp. nov. is characterized for possessing a spicule complement composed by tylostyles, styles, acanthostyles in two size categories, oxychaetes and an encrusting growth form. The most similar species are E. clavilectuarium and E. suassunai which share two categories of acanthostyles, subectosomal styles and choanosomal subtylostyles but they differ from the new species for presenting raphideform styles and spicules dimensions (Tab. 1). The new species is distinguished from E. clavatella Little, 1963, E. clavatum (Bowerbank, 1866), E. coronula (Bowerbank, 1874), E. distyli, E. fulvum Lévi, 1969, E. lacazei (Topsent, 1891), E. longispiculum (Carter, 1876), E. major Sarà & Siribelli, 1960, E. pulitzeri nom. nov., E. radiatum (Bowerbank, 1866), E. toureti (Topsent, 1894) and E. viride (Topsent, 1889) because these species have only one category of acanthostyles. In the species E. lictor (Topsent, 1904) and E. topsenti (Burton, 1954) acanthostyles are absent. E. oxychaetum sp. nov. differ from E. hispidulum (Topsent, 1904), E. incipiens Topsent, 1927, E. mucronale (Topsent, 1928), E. scabiosum (Topsent, 1927), E. simplex (Bowerbank, 1874) and E. urizae (Hooper, 1996), because they do not have subectosomal styles. Eurypon miniaceum Thiele, 1905 and E. mixtum (Topsent, 1928) are distinguished from E. oxychaetum sp. nov. by their spicules dimensions (Tab.1).