Crella (Yvesia) mammillata (Arnesen, 1903) is a papillate lumpy sponge known only from a single record of 50-60 m in Norwegian waters.
Colour: Not recorded.
Shape, size, surface and consistency: Lumpy masses agglutinating pebbles, shells, bryozoans and sand grains. Surface papillate but smooth. Oscules on the papillae. Ectosome not easily detachable. Consistency rather firm but compressible.
Spicules: (Crella mammillata spics) Megascleres: Smooth tylotes: 300-400 x 4 µm; lightly curved styles, smooth or with rugose heads: 200-500 x 6 µm; acanthostrongyles and acanthostyles: 80-160 x 4 µm. Microscleres: Arcuate isochelae: 24 µm.
Skeleton: Ectosomal skeleton consists of a tangential mass of acanthostyles/ acanthostrongyles. Choanosomal skeleton an irregular plumose network of single tylotes and styles.
Ecology: Deeper water, 50-60 m.
Distribution: Known only from Norway (Bödö in the Tromsösund).
Etymology: The name refers to the nipple-like surface papillae.
Type specimen information: Type is presumably in the Bergen Museum.
Its spiculation is unusual in the combination of tylotes and styles as choanosomal megascleres.
Source: Arnesen (1903)