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The sponge genus Ephydatia from the high-latitude middle Eocene: environmental and evolutionary significance - PubMed

The sponge genus Ephydatia from the high-latitude middle Eocene: environmental and evolutionary significance

Andrzej Pisera et al. Palaontol Z. 2016.

Abstract

The freshwater sponge species Ephydatia cf. facunda Weltner, 1895 (Spongillida, Spongillidae) is reported for the first time as a fossil from middle Eocene lake sediments of the Giraffe kimberlite maar in northern Canada. The sponge is represented by birotule gemmuloscleres as well as oxea megascleres. Today, E. facunda inhabits warm-water bodies, so its presence in the Giraffe locality provides evidence of a warm climate at high latitudes during the middle Eocene. The morphological similarity of the birotules to modern conspecific forms suggests protracted morphological stasis, comparable to that reported for other siliceous microfossils from the same locality.

Die rezente Süßwasserschwamm-Art Ephydatia cf. facunda Weltner, 1895 (Spongillida, Spongillidae) wird erstmals als Fossil aus den mittel-eozänen Seeablagerungen des Giraffe Kimberlit-Maars im nördlichen Kanada nachgewiesen. Die Schwammspezies ist sowohl durch birotule Gemmoskleren als auch durch Megaskleren (Oxen) belegt. Heute besiedelt E. facunda warm-temperierte Wasserkörper, somit spricht ihr Vorkommen für ein warmes Klima in hohen Breiten während des Mittel-Eozäns. Die morphologische Ähnlichkeit der Birotulen in Bezug auf moderne konspezifische Formen legt eine protrahierte morphologische Stasis nahe, vergleichbar mit derjenigen anderer kieseliger Mikrofossilien aus derselben Fundstelle.

Keywords: Canada; Climate; Eocene; Freshwater sponges; Morphological stasis; Porifera.

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Figures

Fig. 1
Fig. 1

Location map and stratigraphy of the Giraffe fossil locality (northern Canada). a Location; b schematic stratigraphy; c lithostratigraphy and Ephydatia cf. facunda spicule occurrences (black vertical bars)

Fig. 2
Fig. 2

Gemmuloscleres of Ephydatia cf. facunda showing the range of morphological variability (strongly modified malformed birotules included). ZPAL Pf.23, SEM, scale bar 10 μm

Fig. 3
Fig. 3

Megascleres belonging to Ephydatia cf. facunda from the Giraffe middle Eocene locality. ZPAL Pf.23, SEM, Scale bar 50 μm

Fig. 4
Fig. 4

Gemmuloscleres morphometries of Ephydatia cf. facunda. Simple plots of rotule size versus length (a) and of shaft thickness of birotules versus length (b)

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