Ephydatia kaiseri Rauff, 1926

Pronzato, Roberto, Pisera, Andrzej & Manconi, Renata, 2017, Fossil freshwater sponges: Taxonomy, geographic distribution, and critical review, Acta Palaeontologica Polonica 62 (3), pp. 467-495 : 482

Ephydatia kaiseri Rauff, 1926

Fig. 15 .

Type horizon: (Pre) middle Eocene freshwater chert.

Type locality: Sinkhole south-west from fixed point 533, Pomona diamond field, Namib Desert, Namibia .

References: Rauff 1926; Arndt 1936; Manconi 2008.

Description (emended from Rauff 1926).—Spiculite of loose spicules with entire gemmules. Megascleres (many broken) oxeas of two dimensional classes, smooth, slightly bent, pointed, sometime with evident axial canal. Large oxeas (350 × 7–17 μm) maybe longer but broken. Short oxeas (up to 20 × 3.5 μm). The shorter and very thin can be young or larval spicules. Gemmules entire, with gemmuloscleres in natural arrangement. Gemmuloscleres birotules (44–65 μm in length) with smooth rotules (18–20 μm in diameter), with entire (not incised) margins, flat except for umbone, and smooth shaft (5–6 μm in thickness).

Remarks.— Ephydatia kaiseri is the only known fossil freshwater sponge from Africa. Rauff (1926) reports loose oxeas and gemmules with birotules in natural arrangement as confirmed by Arndt (1936: 17). The original paper reports that the deposit mainly consists of sponge spicules; in about 1– 0.5 mm 2 there are a minimum 70 of relicts. The spicules consist of chalcedony, however, some rare spicules do not show a double refraction. The variable length of birotules matches the dimensional spectrum of known species of extant Spongillidae belonging to the genus Ephydatia . The identification at the species level is confirmed by Manconi (2008). The Recent species Ephydatia fluviatilis var. capensis Kirkpatrick, 1907 reported from the Cape region (Valkenberg Vlei, South Africa) is in part similar to E. kaiseri sharing with it some birotules with smooth rotules, flat except for umbone, with margins not incised, and smooth shaft (see Manconi and Pronzato 2009: 133, figs. 163–165). Spongillidae Gray, 1867

Figures

Fig. 15. Ephydatia kaiseri Rauff, 1926, Spongillida: Spongillidae; (pre) middle Eocene freshwater chert, Pomona diamond field, Namib Desert, Namibia. A. Grouped gemmuloscleres; originally enlarged 660×, the text states that particular birotules are 44–65 μm long. B. Megascleres; originally enlarged 175, the text states that spicules are 350 μm long. C. Birotule (gemmulosclere), originally enlarged 660×, the text states that spicule can be 44–65 μm long. D. Gemmule of a Recent species of Ephydatia (cross section). A, B, photographs; C, D, schematic drawings. Modified from Rauff (1926).