Dynamics of placoderm distribution in the Prague Basin (Czech Republic)

Abstract

The occurrence of placoderms in the Prague Basin (Bohemian Massif; Czech Republic) shows a very unsteady distribution in space and time. The most abundant specimens are in the Lochkovian and, through decrease in the Pragian, they become rare towards the Givetian. The primitive acanthothoracids dominating in the Lochkovian and Pragian are completely replaced by arthrodires at the beginning of the Emsian. All placoderms in the Prague Basin, without any regard to their dimensions, had smooth jaws which is a proof of their non-predatory feeding habit. Although placoderm diversity is generally considered to reflect the Devonian nekton revolution, the abundance of these vertebrates in the Prague Basin displays a decrease, i.e. an inverse tendency to the global one.

Unique diversity of acanthothoracid placoderms (basal jawed vertebrates) in the Early Devonian of the Prague Basin, Czech Republic: A new look at Radotina and Holopetalichthys

“…The Černá rokle quarries yielded the most abundant placoderm material, greatly exceeding the number of specimens from the remaining localities of the Prague Basin [31]. It is uncertain whether this abundance is a taphonomic effect, the result of intensive collecting of all fragments during the period of active quarrying, or if the placoderms were genuinely more abundant in the Lochkovian of the Prague Basin.…”

“…Numbers represent the fossil sites: 1 Černá rokle near Kosoř; 2 Koněprusy. Modified from [31] after [41]. …”

“…Most of the specimens are now housed in public collections (Národní Muzeum (National Museum) in Prague, Czech Geological Survey and the Faculty of Science, Charles University). The collections can be considered as non-selective because almost all the rare specimens were included [31]. The best preserved remains were discovered in the period of active, especially manual quarrying in the Prague Basin (see below).…”

“…The last extensive study of the Lower Devonian material from the Bohemian collections by Westoll [37] was focused on morphological terminology and phylogenetic relationships rather than taxonomy of the studied material. No other attempt to revise the Prague Basin placoderm material had been made prior to the recent studies by one of the current authors [31,38,39]. …”

Vertebrate Microremains from the Pragian, Emsian and Eifelian of the Prague Basin (Czech Republic)

“…Cross-sections of fin spines and fine superficial structures of preserved dermal plates, scales, or fin spines were figured by Barrande 1872;pls 28, 30. His determinations were revised since (Eastman, 1897;Bayer, 1905) and later new vertebrate remains from the Barrandian area were described or reviewed (von Koenen, 1895;Růžička, 1929;Gross, 1950Gross, , 1958Gross, , 1959Gross, , 1973Vaškaninová & Kraft, 2014a, 2014bVaškaninová & Ahlberg, 2017).…”