paradox

Vol 57, No 1-2 (2023)

Authors: Jaroslav Marek, Radko Šarič & Petr Kácha

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 Abstract: As yet undescribed accumulations of shells of orthoconic cephalopods, which are in someAs yet undescribed accumulations of shells of orthoconic cephalopods, which are in someaspects comparable to cephalopod limestones known from the Silurian and Lower Devonian of theBarrandian area and other regions of the world, occur in the Letná and Zahořany formations (middleSandbian and lower Katian stages, Upper Ordovician, central Bohemia). These accumulated shells areoften colonized by sessile organisms. Only a small proportion of these organisms could be attachedto shells of alive cephalopods; the majority of them used empty shells as solid substrates. The mostabundant epizoan is the cystosporate bryozoan of the genus Ceramopora that often overgrows the cephalopodshells extensively. Holdfasts of the genus Sphenothallus and problematic fossils assigned to the genus Conchicolites are common. Rarer epibionts include the bryozoan Spatiopora, the cystoid echinoderm Codiacystis and the brachiopod Ptychopeltis. Varying sizes of bryozoan colonies occurring on the samecephalopod shell point to several recurring attachment events, probably reflecting reproduction cycles.

Authors: Michal Mergl

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 Abstract: The new material of conulariids is described from the mid-Sheinwoodian “Miraspis Limestone”The new material of conulariids is described from the mid-Sheinwoodian “Miraspis Limestone”at the famous Špičatý vrch locality near Loděnice in the Barrandian area. Although poorlypreserved, three taxa have been determined, referred to the Archaeoconularia cf. fecunda (Barrande, 1855),Conularia proteica Barrande, 1854 and Metaconularia (?) sp.

Authors: Jaroslav Marek, Radko Šarič & Petr Kácha

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 Abstract: In the middle Sandbian and lower Katian (Upper Ordovician) rocks of the Barrandian area,In the middle Sandbian and lower Katian (Upper Ordovician) rocks of the Barrandian area,the fossil remains of conulariids are relatively abundant. Their thecae were sometimes used as solid surfacesfor the attachment of epizoans, mostly craniid brachiopods of the genus Petrocrania, more rarelyalso echinoderms Hemicystites and Agelacrinites, and bryozoans Ceramopora and Spatiopora. The orientationof shells of Petrocrania suggests that conulariids (mostly belonging to the genus Archaeconularia) were dead at the time of the brachiopod attachment, their thecae were partly fragmentary and secondarilyreplaced. A find of Pseudoconularia grandissima attached to the theca of the cystoid Codiacystis is alsoreported.