Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)

Paleontological research in an important locality of the Rudník Horizon (Lower Permian) in the Krkonoše Piedmont Basin


Stanislav Štamberg

Geoscience Research Reports 49, 2016, pages 27–30
Map sheets: Semily (03-41)

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Published online: 23 May 2016

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Results of an extensive research in the locality Rybnice "Hrádecký creek" (coordinates 50o37´57.060"N; 15o24´30.469"E) are presented. Artificial outcrops of a lacustrine bituminous grey-black calcareous claystone are a part of the Rudník Horizon (Tásler et al. 1981; Prouza et al. 2013), which belongs to the Vrchlabí Formation (Lower Permian, Asselian). Martínek et al. (2006) used the term Rudník Member for that thick set of lacustrine beds. Initially minute outcrops along the right bank of the Hrádecký creek were artificially enlarged in two close outcrops (2.5 × 2.0 metres in ground plan) on the right side and in the watercourse of Hrádecký creek (Figs 1, 2). The bed with fossils is a 164 cm thick organic rich grey-black calcareous claystone. Due to its mechanical toughness, the rock was cut with a grinding machine to blocks of approximately 60 × 60-80 cm, and 8-10 cm thick (Fig. 2); these blocks were subsequently splintered into smaller fragments.
Actinopterygians are the most abundant in the locality, and specimens of the genus Paramblypterus form more than 95% of all finds of actinopterygians. Bones and scales of Paramblypterus are morphologically variable, as is their sculpture, but probably only the species Paramblypterus rohani (Heckel, 1861) is present (Fig. 3B). Aeduellid species Neslovicella elongata Štamberg, 2010 is much rarer, and such specimens from this locality were studied recently (Štamberg 2010). Quite rare are small carnivorous actinopterygian, whose morphology of bones, and sculpture of bones and scales evoke the genus Letovichthys Štamberg, 2007, originally described from the Lower Permian of the Boskovice Graben (Štamberg 2007). Acanthodians are relatively abundant, and some specimens studied by Zajíc (2005) were assigned to Acanthodes gracilis (Beyrich, 1848) and Acanthodes sp. (Fig. 3A). Xenacanthid sharks of the genus Bohemiacanthus sp. (Fig. 3C), and rarely Triodus sp., occur throughout the section of the fossiliferous organic rich grey-black calcareous claystone. Occipital spines, as well as whole specimens were found, one of which exceeds 90 cm in length. Amhibians are rare, and only 5 skeletons of small branchiosaurs were discovered until now; it is possible to assign one of them to the genus Melanerpeton Fritsch, 1878.
Research of the locality has been going on for several years, and has produced a comprehensive view of Lower Permian faunas of the Rudník Horizon (Vrchlabí Formation, Asselian). The collection of fossils, particularly of actinopterygians, obtained in the excavations is an excellent source of material for subsequent anatomical and taxonomical studies.