Ephydatia gutenbergiana (Muller, Zahn, and Maidhof, 1982) Megascleres. Oxeas

Pronzato, Roberto, Pisera, Andrzej & Manconi, Renata, 2017, Fossil freshwater sponges: Taxonomy, geographic distribution, and critical review, Acta Palaeontologica Polonica 62 (3), pp. 467-495 : 483-484

Ephydatia gutenbergiana ( Müller, Zahn and

Maidhof, 1982)

Fig. 16 .

Type horizon: Middle Eocene.

Type locality: Messel, Germany. References: Müller et al. 1982; Richter and Wuttke, 1995; Richter and Baszio 2000, 2001, 2009; Richter et al. 2017.

Description (emended from Müller et al. 1982).—Megascleres oxeas of two dimensional classes (140–230 × 15–20 μm; 200–350 × 10–20 μm). Gemmuloscleres similar smaller oxeas (50–150 μm in length). Gemmules (structure interpreted as) with an extremely large diameter> 2 mm.

Redescription (emended from Richter and Wuttke 1995; 1999).—Unordered masses of gemmuloscleres heavily corroded and partially bounded together, and surrounded by secondary precipitation of dissolved silica. Absence of most of the rotules due to quite advanced corrosion processes. Spines as corrosion pits in the few spicules with rotules still recognizable.

Remarks.—According to the type material re-examination, the evaluation by Richter and Wuttke (1995, 1999) of the studied spicular complement is quite different from Müller et al. (1982). Gemmuloscleres found by the former authors in the holotype are birotules, whereas those by the latter are short spiny oxeas typical of Spongilla . Even the size of gemmules described by Müller et al. (1982) suggests that they cannot be considered true gemmules, as the largest known Spongillida gemmular diameter is only slightly larger than 1 mm. The new gemmuloscleres, found in the spiculite by Richter and Wuttke (1995, 1999) and Richter and Baszio (2009) are interpreted as birotules radially arranged in the gemmular theca of a species belonging to the genus Ephydatia . Indeed gemmuloscleres are spiny oxeas in Spongilla and birotules in Ephydatia . The new combination proposed by Richter and Wuttke (1995) shifting the species S. gutenbergiana to the genus Ephydatia is illustrated by quite convincing SEM images. The taxon could be a mix of species and further studies are needed.

Figures

Fig. 16. Ephydatia gutenbergiana (Müller, Zahn, and Maidhof, 1982), Spongillida: Spongillidae; middle Eocene, Messel, Germany. A. Five oxeas as represented in the original description. B. Entire gemmule. C. Skeletal network (line-like arranged megascleres). D. Megascleres. E. Gemmuloscleres, the transitional forms of the series a (bottom, right) could point out an origin of the birotules from oxeas with shortened shaft. F. Corroded gemmuloscleres. G, H. Two illustrations of gemmuloscleres that has been shifted from the genus Spongilla to the genus Ephydatia; insert in H shows gemmulosclere in phase contrast. I. Megasclere, original material with corrosion marks that are characteristic for Messel. Modified from: A, Müller et al. (1982); B, F, Richter and Wuttke (1999); G, H, Richter and Wuttke (1995); I, Richter and Baszio (2009).