Aphroceras Gray, 1858

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 : 225-227

Genus Aphroceras Gray, 1858

TYPE SPECIES. — Aphroceras alcicornis Gray, 1858 by monotypy.

DIAGNOSIS. — Grantiidae with a leuconoid organization. The cortex is supported, at least in part, by giant longitudinal diactines.

DESCRIPTION

Aphroceras is differentiated from Leucandra by the presence of internal longitudinal diactines in the cortex (Fig. 22). In a previous study (Borojevic 1966), it was shown that the number of these spicules can be quite variable, ranging from a continuous dense layer to only very rare spicules, or even absence. In the latter case, it is not possible to distinguish this sponge from a typical Leucandra . However, we retain this genus at present, as we feel that the typical Aphroceras are easy to identify. Dendy & Row (1913) pointed out that Aphroceras probably derives directly from Leucandra by a secondary acquisition of longitudinal internal diactines, and not from Ute by a modification of the syconoid DESCRIPTION

Leucandrilla is differentiated from Leucandra by the presence of tetractines in the cortical skeleton ( Fig. 23 ). Like Aphroceras , which is distinguished from Leucandra by the presence of cortical diactines, the separation between Leucandrilla and Leucandra is not clear-cut. Dendy (1913), Dendy & Row (1913) and Borojevic & Boury-Esnault (1987) have already pointed out that some of the sponges with cortical tetractines that had been classified among Amphoriscidae are not very different from a typical Leucandra , but are quite distinct from Leucilla , and should consequently be classified in the Grantiidae . In particular they have a complete articulate choanoskeleton, reminiscent of the grantiid organization, which is absent in Amphoriscidae . While Dendy (1913) proposed that these sponges should be included in Leucandra , we now propose to isolate them in a separate genus in the family Grantiidae , analogous with the recognized separation of Aphroceras . It should be noted that we consider the cortical tetractines in this genus to be a secondary character, corresponding to a modification of normal cortical triactines, while cortical tetractines of the family Amphoriscidae are a primary character, marking an independent evolutionary line.

In addition to L. wasinensis (Jenkin, 1908b) , which we propose to be the type species of the genus Leucandrilla , other sponges that had been classified in the genus Leucandra , such as L. intermedia (Row, 1909) and L. lanceolata (Row & Hôzawa, 1931) , also belong to this genus.

Figures

FIG. 23. — Leucandrilla organization. Section made on the type specimen from Jenkin (1908b) (BMNH 1908.9.25.59).The cortex contains tetractines (t), with the apical actines turned into the choanoderm. Scale bar: 150 µm.