Sponge spicules and radiolarians from the Olešná Member of the Klabava Formation (Ordovician, Prague Basin, Czech Republic)

Abstract

Abundant, morphologically moderately diverse, and well-preserved hexactinellid sponge spicules, mostly pentactines and hexactines, were collected from the lower Olešná Member of the Klabava Formation (Arenigian) of the Komárov area, Prague Basin. Demosponges, represented by lithistiid dendroclones and the large radiolarian genus Anacrusa, were identified in the acid-etched residue of (?) phosphatic clasts. The species Pyritonema feistmanteli is critically revised. •

The hexactinellid sponge Cyathophycus from the Lower Ordovician Klabava Formation of the Prague Basin, Czech Republic

“…The size and morphology of the spicules in Cyathophycus sp. are identical with the large pinnate pentactines isolated from the phosphatic clasts in the lower part of the Olešná Member and described by Mergl & Duršpek (2006; Fig. 2D).…”

“…indet. A" by Mergl & Duršpek (2006). Among the material described by Mergl & Duršpek (2006) are also present smaller pentactines and small thickrayed hexactines.…”

“…A" by Mergl & Duršpek (2006). Among the material described by Mergl & Duršpek (2006) are also present smaller pentactines and small thickrayed hexactines. These differently sized spicules possibly belong to different ranks of spicules indicating the more complex and multilaminar body wall of another reticulosid.…”

“…The diversity and detailed morphology of these spicules has recently been revealed (Mergl & Duršpek 2006) but the general shape of the sponges and their spicule arrangement have remained unknown. A unique cluster of spicules has been observed in the palaeontological collection in the National Museum, Prague, a specimen collected by Celda Klouček some 80 years ago.…”

Paraconodont Westergaardodina in the Lower Ordovician of the Prague Basin, Czech Republic

“…The associated organophosphatic brachiopods are remarkably well preserved (Mergl 2002), although their original shell has been partially replaced by silica, leaving small empty spaces between thin external and internal silica sheets. The siliceous sponge spicules are well-preserved (Mergl & Duršpek 2006). The degree of preservation of the Westergaardodina elements is somewhat puzzling: they show a similar mode of preservation as the brachiopod shells, but other conodonts are absent.…”