Problematic Sclerites Eurytholia from the Lower and Middle Devonian of the Czech Republic

Abstract

Problematic phosphatic sclerites Eurytholia are reported for the first time from the Middle Devonian. Unequivocal sclerites were observed in limestones of Emsian to late Eifelian age in six localities of the Barrandian area of the Central Bohemia of the Czech Republic. Formerly observed size and shape variations of Eurytholia sclerites prevent formal description of a new species on few specimens of Emsian and Eifelian age. Therefore the new specimens are identified as Eurytholia aff. bohemica. Their presence indicates longer time range of the Eurytholia animal, covering not only the Ordovician, the Silurian and the earliest Devonian as known formerly, but also late Lower Devonian and the Middle Devonian. Similar features in morphology and histology of Eurytholia indicate relationship to a conodont Pseudooneotodus and a support suggestion about the vertebrate origin of Eurytholia sclerites.

Byronids and similar tubular fossils from the Devonian of the Barrandian area (Czech Republic)

“…2017), conodonts, conulariids (Mergl et al . 2016), problematic fossil Eurytholia (Mergl 2019b), phyllocarid remnants and byronids were observed in residues. Conodonts indicate the lower part of the Polygnathus serotinus Zone.…”

“…Thin-bedded nodular dark-grey micritic limestone of the Basal Choteč Event yielded rhynchonelliform brachiopods, mostly chonetids and small strophomenids (Havlíček 1977; Havlíček & Racheboeuf 1979). Organophosphatic linguliform brachiopods (Mergl 2001; Mergl & Vodrážková 2012), small spines of phyllocarid crustaceans, acanthodian scales, conodonts, problematic fossil Eurytholia (Mergl 2019b), prasinophytes, and rare tubes and discs of byronids were observed in residues. Conodonts indicate the lowermost part of the Polygnathus costatus Zone (summarised by Berkyová 2009; Vodrážková et al .…”

“…Phosphatic fossils are represented by minute linguliform brachiopods (Mergl 2019a), fish scales, teeth and bones (Mergl et al . 2017), problematic fossil Eurytholia (Mergl 2019b), diverse conodonts (Vodrážková & Suttner 2020), and rare byronid tubes and discs. The dark interval has been correlated with the Kačák Member (Hladil et al .…”

Little pieces of mystery from the Silurian of the Dingle Peninsula, Ireland

“…The genus Eurytholia had been introduced from the Middle-Upper Ordovician of the Iapetus Ocean (United Kingdom, Sweden, Estonia and Alabama) for a problematic scleritome, ovoid in outline, with protective plates inserted in soft tissue along sub-longitudinal rows (Sutton et al 2001). Other isolated plates were re-ported from the Silurian to Middle Devonian of the Czech Republic (Ferretti et al 2006;Mergl 2019), the Silurian of the Carnic Alps (Ferretti and Serpagli 2008) and the Silurian-lowermost Devonian of Sardinia (Corradini et al 2009b). Mergl (2019) recently proposed a vertebrate origin for the Eurytholia sclerites, remarking the affinity with the conodont Pseudooneotodus.…”

“…Other isolated plates were re-ported from the Silurian to Middle Devonian of the Czech Republic (Ferretti et al 2006;Mergl 2019), the Silurian of the Carnic Alps (Ferretti and Serpagli 2008) and the Silurian-lowermost Devonian of Sardinia (Corradini et al 2009b). Mergl (2019) recently proposed a vertebrate origin for the Eurytholia sclerites, remarking the affinity with the conodont Pseudooneotodus.…”