Vertebrate microremains from the upper Silurian Winnica Formation of the Holy Cross Mountains, Poland

Abstract

Vertebrate microremains from the upper Silurian Winnica Formation in the Holy Cross Mountains, Poland are described from the Winnica and Rzepin sections. Both sites record the uppermost part of the Słupianka Member, but represent different depositional environments. The Winnica samples come from a low-energy environment, while the Rzepin sample was taken from a high-energy, oolitic facies. Both sites contain thelodontsThelodus parvidens,Thelodus trilobatus, an anaspid cf.Liivilepisand a number of acanthodian scales of ‘nostolepid’, poracanthodid and ‘gomphonchid’ types. Notable differences between the sites are the addition of the osteostracanTahulaspiscf.ordinata, the thelodontParalogania ludlowiensisand acanthodian scales identified asNostolepis gracilisin the Rzepin section. Placing the vertebrate faunas within the vertebrate biozonation established for the Silurian proved difficult. The suggested late Ludlow age for the Słupianka Member based on sequence stratigraphical and chemostratigraphical correlations cannot be definitely confirmed or refuted, but a late Ludfordian age seems the most plausible based on invertebrate and vertebrate faunas. The much lower abundance of poracanthodid acanthodians in the Rzepin sample supports the notion ofPoracanthodes porosusZone as a deep-water equivalent to a number of vertebrate biozones. The presence ofP. ludlowiensisonly in the oolitic sample confirms a long temporal range, but restricted environmental distribution for this taxon.

Vertebrate remains and conodonts in the upper Silurian Hamra and Sundre formations of Gotland, Sweden

“…A sample from the Winnica site contained thelodonts Thelodus parvidens, T. trilobatus, and anaspid fragments similar to Liivilepis. The range of "nostolepid" and "gomphonchid" acanthodian scales were similar to those described here, but the poracanthodid scale-variants were more abundant (Bremer et al 2017). The other sample came from an oolitic layer of potentially slightly younger age than the Sundre Formation at the top of the Rzepin section, and displayed a more similar fauna to Gotland regarding abundance of acanthodians, as well as a few fragments of an osteostracan similar to Tahulapsis ordinata (Bremer et al 2017).…”

“…Furthermore, a huge difference in the abundance of trilobatiform scales have been observed in largely coeval samples from different environmental settings in the Holy Cross Mountains of Poland. More than a hundred scales were recovered from one sample but only five scales were found in the other one, while the number of typical parvidens-type scales remained fairly constant in both (Bremer et al 2017). This is surprising if they indeed come from the same species.…”

“…obs. 2019), and it has been proposed that its distribution is fairly limited to similar lithologies (Kaljo et al 2015;Bremer et al 2017). A possible exception to this is sample A912SF, which also contains several typical scales of P. ludlowiensis, but is labelled as coming from the Hoburgen Lighthouse and was listed as "Sundre/Hamra-kalk" in Alberti's stratigraphical chart.…”

“…The early vertebrate remains in samples from two different sections of the upper Słupianka Member (Winnica Formation) in the Holy Cross Mountains, Poland, were described in Bremer et al (2017). These strata have been suggested as largely coeval with the Hamra and Sundre formations on Gotland based on chemo-and sequence stratigraphy, but they were deposited on the opposite side of the Baltic Basin (Kozłowski & Munnecke 2010).…”

“…The Silurian strata of Gotland, Sweden, display rich vertebrate assemblages throughout most of the sequence (e.g., Fredholm 1988aFredholm , 1988bFredholm , 1989Fredholm , 1990Eriksson et al 2009;Jarochowska et al 2016a;Bremer 2017). The most extensive works on Gotland vertebrates to date are those by Fredholm (1988aFredholm ( , 1988bFredholm ( , 1989Fredholm ( , 1990, but the only report on vertebrates from the youngest parts of the Gotland stratigraphy was made by Fredholm (1989).…”