Nodastrella, gen. nov.

Nodastrella gen. nov.

Synonymy: Asconema in part (van Soest and Lavaleye 2005: Fig. 2 A–B); Rossella in part (Topsent 1915: 1, Figs. 1–5; Topsent 1928: 76, Pl. III Fig. 22, Pl. IV Fig. 3; Tabachnick and Collins 2008: Fig. 15).

Type species: Nodastrella nodastrella (Topsent).

Definition: Saccular Rossellinae with both calycocomes and discasters among microscleres, microdiscohexasters concentrated near the dermal surface, and dermalia chiefly stauractins.

Diagnosis: Basiphytous saccular Rossellidae barrel- to amphora-shaped, with a large atrial cavity ending in a wide, unfringed, central osculum, with everted marginal parts in older specimens. Colour in life is white to greyish. Choanosomal main skeleton chiefly of diactins combined with intermediate hexactins and pentactins, dermalia are microspined stauractins and few pentactins, tauactins, and diactins, hypodermalia are large orthotropal pentactins, gastralia mainly hexactins, but also include pentactins, stauractins, and tauactins. Prostalia lateralia, if present, are diactins. Microscleres are calycocomes with reduced primary rays, spherical discasters, microdiscohexasters, (hemi)oxyhexasters, oxyhexactins, and rare onychohexasters. Discasters are concentrated near the atrial surface, microdiscohexasters are concentrated near the dermal surface.

Remarks: The skeleton of Nodastrella is similar to that of Rossella in the presence of calycocomes, although they are different in morphology by showing reduced primary rays and a central swelling. It differs from Rossella mainly by its dermalia, which are chiefly stauractins (whereas the dermalia of Rossella are chiefly pentactins), the presence of discasters (never found in Rossella), and the absence of tyloidal and rhopaloidal microscleres, discohexactins, and anisodiscohexasters, the latter a typical spicule of most Rossella species (although missing in R. antarctica Carter and R. levis (Kirkpatrick)). Furthermore, the concentration of macrodiscohexasters near the atrial surface and microdiscohexasters near the dermal surface is unique within Rossellidae; in Rossella the distribution of microscleres is opposite to that of Nodastrella (see also van Soest et al. 2007). A further difference is the presence of some stauractins and tauactins and the absence of diactins among the atriala (in Rossella, some diactins can be present whereas stauractins and tauactins are absent).

To accomodate removal of nodastrella from Rossella, we here provide emended definition and diagnosis for the latter genus (from Tabachnick 2002a; additions highlighted in boldface):