Aaptos lobata

Description. The sponge is massive, sub-spherical or lobate (Fig. 2 A, B). The holotype (Fig. 2 A) is a fragment about 1.5 cm long and 1 cm thick, sampled from a large globular specimen; the paratype is a small portion, approximately 2.5 cm long and 1 cm thick, of a large cushion-shaped specimen approximately 60 cm across. The paratype (Fig. 2 B) shows a sort of lobate organisation, with roundish parts connected by bottleneck narrowings. The colour in life is yellow, varying between orange and brown according to light exposure; it is not uniform, but presents dark red spots or stripes (Fig. 2 A, B). The sponge is always yellow inside. Alcohol-preserved specimens are dark green-brown. The sponge surface is smooth, but microscopically hispid. Ostia, grouped in distinct areas on the sponge surface, have such a large diameter that they are visible to the naked eye. Oscula are flush, more or less circular, with a very low rim. Converging exhalant canals are visible in their lumen (Fig. 2 A). Consistency is hard when preserved. Skeleton. The choanosomal skeleton is radiate, regular in the outer part of the sponge and more irregular in the deeper part. Due to high spicule density, spicule tracts are not easily detectable (Fig. 2 C, D). In the ectosome, the smallest styles are arranged in palisade and do not form brushes, whereas the spicules of intermediate size are concentrated in the sub-ectosomal layer and protrude through the surface with their tips (Fig. 2 C, D). Abundant spheroulous cells, approximately 12 µm in diameter, are detectable in the choanosome. Spicules. Three size categories of megascleres, partially overlapping at the extremities of their size-frequency distributions. The larger spicules are straight strongyloxeas with acerate or slightly stepped tips (Fig. 2 E) and often evident axial canal. Intermediate and small megascleres, straight or slightly curved, vary in shape from strongyloxeas to subtylostyles to thin styles (Fig. 2 F). The measurements are given in Table 2.