A Large Predatory Arthrodire (Vertebrata, Placodermi) from the Famennian (Upper Devonian) of the Holy Cross Mountains, Poland

The remains of Late Devonian placoderms from the Holy Cross Mountains area have already been established and widely recognized thanks to the diligent studies of GorizdroKulczycka (1934) and Kulczycki (1957) and more recently by Ivanov and Ginter (1997) and Szrek (2020, and references therein). Huge predatory arthrodires are known from the Frasnian of Płucki, within Kielce County, Świet̨okrzyskie (Holy Cross Mountains) Voivodeship, in south-central Poland and are represented by Dunkleosteus (specimen Muz. PGI-NRI 1809.II.18) with a head measuring 60 cm in length (Szrek and Wilk, 2018). In addition, remains of a massive Titanichthys (now regarded as a suspension feeder; Coatham et al., 2020) are described from the Famennian in the nearby village of Gałez̨ice (Kulczycki, 1957). The investigated material originates from Kowala (Fig. 1), an active quarry located about 15 km south of Kielce at the eastern part of the Gałez̨ice Syncline. The locality has served as a key source area for fossils to many authors such as Szulczewski (1971), Czarnocki (1989), Racki (1998, 1999), Racki et al. (2002), Bond and Zaton ́ (2003), Bond et al. (2004), Marynowski and Filipiak (2007), Kazḿierczak et al. (2012), Malec (2014) and Zaton ́ et al. (2014). Currently this site represents the most complete Middle-Upper Devonian to lowermost Carboniferous section exposed in Poland. In the Late Devonian, the southernmost region of the Polish Holy Cross Mountains was located in a subtropical zone at the southern edge of Laurussia. The entire area was covered by a shallow, epicontinental sea. An extensive shallow carbonate platform dominated the western part of the region. The eventual disintegration of this platform, which began in earnest at the end of Middle Devonian, resulted in considerable environmental and ecosystem diversity (Szulczewski, 1995). In the late Frasnian, the carbonate platform became fragmented with sedimentation becoming uniform over most of the area, with the deposition of marls, marly shales and shales, except for a few isolated places (Szulczewski, 1971, 1973, 1995; Szulczewski and Żakowa, 1976; Bełka and Skompski, 1988). The Famennian succession, as expressed by themarls and shales, shows progressive stepwise submersion of the carbonate platform up to the Carboniferous. The Famennian in Kowala consists of dark-gray laminated marls and bituminous marly shales intercalated by horizons of nodular or thin bedded micritic-marly limestones (for a complete section log see Szulczewski, 1971, 1995; Berkowski, 2002; Malec, 2014). The rocks contain locally abundant fossils including cephalopods (Czarnocki, 1989; Dzik, 2006), the pseudoplanktonic bivalve Guerichia and planktonic entomozoacean ostracodes (Olempska, 1997). The benthic fauna occurs in a single horizon and is represented by monospecific small solitary rugose corals (Berkowski, 2002), brachiopods (Biernat and Racki, 1986; Halamski and Balinśki, 2009), eye-less trilobites (Radwanśki et al., 2009), tabulates (Zapalski et al., 2016), bryozoans, fish remains (Ginter and Piechota, 2004), conodonts (Szulczewski, 1971; Dzik, 2006), and echinoderm debris. The general sedimentary environment of the Famennian Kowala succession is interpreted as a pelagic, periodically anoxic, dysphotic (Szulczewski, 1971, 1995; Biernat and Racki, 1986; Halamski and Balinśki, 2009) relatively deeper-water environment with soft muddy, dysaerobic bottom conditions (Berkowski, 2002). Poor oxygenation of the bottom water probably resulted from density stratification of the water column and sluggish circulation within the basin (Olempska, 1997). In addition, the succession contains the record of several globally recognized anoxic oceanic events (Joachimski et al., 2001; Marynowski and Filipiak, 2007), i.e., lower and upper Kellwasser (Joachimski et al., 2001), annulata (Racka et al., 2010), Dasberg (Marynowski et al 2010), and Hangenberg (Marynowski et al., 2012).