Polymastia Bowerbank 1864

• Main Authors: Plotkin, Alexander S., Janussen, Dorte
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2008
• Subjects: Biodiversity; Taxonomy; Animalia; Porifera; Demospongiae; Hadromerida; Polymastiidae; Polymastia; Antarc*; Antarctic
• Online Access: https://doi.org/10.5281/zenodo.6235791; http://treatment.plazi.org/id/03E887DC5E6DFFB75EC91608FDF2ADC5

Genus Polymastia Bowerbank, 1864 Diagnosis (emended from Boury­Esnault 2002): Thickly encrusting sponges of spherical, hemispherical or cushion shape, always with papillae. Choanosomal skeleton is composed by radial tracts of principal spicules between which free spicules are scattered. Cortical skeleton constituted by at least two layers, the superficial palisade of small tylostyles and the lower layer made of intermediary spicules, lying tangential to the surface. The principal spicules can be tylostyles, subtylostyles, styles, and strongyloxeas, intermediary spicules are most often tylostyles, and cortical spicules are always tylostyles. Remarks to diagnosis: At the moment 73 from 117 accepted polymastiid species are placed in Polymastia (van Soest et al. 2005), and some of them demonstrate noticeable discrepancies with the currently accepted diagnosis of the genus (see, e.g. Kelly­Borges & Bergquist 1997), that calls for its considerable re­evaluation. Since we did not aim to revise Polymastia in the present study, the emendations of the diagnosis given in Systema Porifera (Boury­Esnault 2002) are minimized. Meanwhile, two Antarctic species, P. invaginata Kirkpatrick, 1907 and P. zitteli (Lendenfeld, 1888), concerned below, bear the features which somehow contradict the accepted diagnosis of Polymastia , the contradiction has not been previously emphasized. The dissimilarities include a single­layered cortex of the former species and the reticulated choanosomal skeleton of the latter. However, as the species in question share some other diagnostic features of Polymastia , we retain them as is, until the revision of the whole genus can be completed. Type species: Spongia mamillaris Müller, 1806 (by monotypy). Polymastia invaginata Kirkpatrick, 1907 (Figs. 4–5, Tables 2–3) Synonymy Polymastia invaginata — Kirkpatrick 1907: 271; 1908: pp. 15–16, pl. XII(1b), pl. XIV (5–15a); Burton 1929: 446; 1932: 338; Koltun 1964: 26, pl. IV(10–14); 1976: 168; Boury­Esnault and van Beveren 1982: 36 –37, pl. IV (13–14), ...