Plectroninia, Hinde, 1900

Borojevic, Radovan, Boury-Esnault, Nicole & Vacelet, Jean, 2000, A revision of the supraspecific classification of the subclass Calcaronea (Porifera, class Calcarea), Zoosystema 22 (2), pp. 203-263 : 260

.............................................. Plectroninia

— Basal skeleton with ascending radial lines .............................................. Petrostroma enclosed within the calcareous skeleton (Vacelet 1964, 1990) ( Fig. 53 ). The skeleton is formed by a solid mass of calcite consisting of elongated sclerodermites that form a series of crests between which lies the living tissue. Spicules trapped within the massive skeleton do not dissolve ( Fig.54 ). The massive skeleton differs in microstructure from that of Murrayona in the Calcinea. The species is known from both living and fossil specimens from Pleistocene strata in the Mediterranean.

Figures

FIG. 53. — Diagram of the organization of Petrobiona massiliana Vacelet & Lévi, 1958. Abbreviations: cx, cortical skeleton; ch, choanosome; ct, tracts of storage cells; d, solid calcareous skeleton; e, parasitic excavating sponge (from Vacelet 1964).

FIG. 54. — Surface view of the solid calcareous skeleton of Petrobiona massiliana, showing terminal spines of the sclerodermites (sc) and partially entrapped spicules (sp) (SEM). Scale bar: 50 µm (from Vacelet 1991).