Description

Description: The holotype is a fragile, lace-like, encrusting sponge, attached to a rock (Fig. 3 A). It was originally 45 mm long, 25 mm wide and 2 mm in height. It has a smooth velvety surface, with no remaining obvious oscules. The aquiferous are clearly visible through the transparent ectosome. The prevalent circular ostia form rows on the surface (Figs. 3 A, B). They are 0.3 mm in diameter, often with protective sharp tips from the styles and (Fig. 3 B, C). The areas between the ostia are visible as semitransparent lines where the spicules are not clustered, giving the appearance of a suburban street network (Fig. 3 A). The sponge is white and translucent on deck and after preservation. The paratype QM G 326453 is also growing on a rock, but paratype QM G 324761 is growing on on Solenosmilia variabilis. Skeleton: The ectosomal skeleton is composed of tangential styles, arranged in a multispicular reticulated pattern around the circular ostia. The supportive styles from the choanosome pass through the ectosomal layer to provide a protective perimeter around the ostia. The small diancistras (II) sometimes occur in the very thin (2 µm) ectosomal layer, where the randomly sparsely scattered styles occur between the ostia. The choanosomal skeleton consists of bundles of ascending twisting columns of styles supporting the ectosomal layer and penetrating through the ectosome to produce the hispid surface (Fig. 3 C). Both diancistras occur in these waisted twisted columns (Fig. 3 C). Spicules: The megascleres are styles, which are abundant, fusiform, straight, sharply pointed, and thickest in the centre (Fig. 3 I). The blunt end is much narrower than the middle and has a rounded style end (see Table 1 for measurements). The large diancistras (I) are common, twisted at about 70 o, the thin sharp fimbriae are very short on the inner shaft on a raised support. The fimbriae on the corresponding face of the hook is easily twice as long. Both faces have such an obvious sharp blade, with the appearance of a razor blade inserted into a razor blade holder (Fig. 3 D). The smaller diancistras (II) are also common, they have sharp opposing alae with a reverse barb, thus resembling a fishhook (Fig 3 F). An example of the reverse barb missing on some of the smaller diacistras was found on one of the specimens (QM G 326453) (Fig. 3 H). Rare examples were found of ‘ teeth’ on the smaller diancistras on one of the specimens (QM G 324761) (Fig. 3 G). The small diancistras only have a small shaft twist of approximately 15 o (Fig. 3 F). The sigmas are rare, thin and have a similar C shape to the small diancistras (Fig. 3 E). One of the paratypes (QM G 324761) also had tylostyles and subtylostyles, but these could not be found in the section and are considered non-native.

Common Names

Taxonomic Hierarchy

Kingdom: Animalia

Phylum: Porifera

Class: Demospongiae

Order: Merliida

Family: Hamacanthidae

Genus: Hamacantha

Species: Hamacantha novacula Ekins & Hooper, 2023