Abstract
A rich assemblage of various marine taxa from the lower Carnian Polzberg Konservat-Lagerstätte near Lunz am See (Northern Calcareous Alps, Lower Austria) is described for the first time in detail. The fossiliferous layers were deposited during the Julian 2 Ib (Austrotrachyceras austriacum Zone, Austrotrachyceras minor biohorizon). The fine-laminated Reingraben Shales comprise abundant and well-preserved members of the marine Carnian food chain. Invertebrates with the bivalve Halobia, the ammonite Austrotrachyceras and the coleoid Phragmoteuthis dominate over vertebrate actinopterygian fishes. Fragile groups such as polychaetes and isopods are entirely preserved as soft body fossils. The diverse assemblage comprises ammonites (Austrotrachyceras, Carnites, Sageceras, Simonyceras), coleoids (Phragmoteuthis, Lunzoteuthis), bivalves (Halobia), gastropods (caenogastropods/heterobranchs), one echinoid, thylacocephalan arthropods (Austriocaris), crustaceans (the decapod Platychela and isopods such as Obtusotelson, Discosalaputium), polychaetes (Palaeoaphrodite sp., eunicid polychaete), acytinopterygians (Saurichthys, Polzbergia, Peltopleurus, Habroichthys), cartilaginous fishes (Acrodus), coelacanth fish (“Coelacanthus”), a lungfish (Tellerodus), and a conodont cluster (Mosherella). Regurgitalites produced by large durophagous fish and coprolites produced by piscivorous actinopterygians accompany the Polzberg palaeobiota along with rare plant remains (Voltzia). The entire fauna of Polzberg and the excellent preservation of the specimens present a window into the Upper Triassic assemblage and palaeoenvironment during the so-called Carnian Pluvial Episode (CPE) in the early Mesozoic. The occurrence of the freshwater lungfish Tellerodus and the branchiopod Eustheria, a member of brackish to freshwater environments, points to the influence of occasional freshwater pulses or sediment transport events on the marine environment. The Polzberg palaeobiota was deposited during the global CPE, triggering the environmental conditions of the Polzberg Basin and resulting in the formation of the Reingraben Shales with the Polzberg Konservat-Lagerstätte.
Highlights
Palaeobiota of fossiliferous sites known as Konservat-Lagerstätte[1] are precious sources of palaeobiological information[4]
We report all known members of the Polzberg palaeobiota, from invertebrates, vertebrates to fossilized bromalites
We argue that a durophagous shark such as Acrodus, which was equipped with a typical durophagous dentition with blunt and broad teeth, most likely produced the studied regurgitalites[5] As noted by Lukeneder et al.[5], the more abundant but smaller and longitudinal coprolites, containing masses of almost exclusively fish scales, were most likely produced by medium-sized piscivorous actinopterygians common in the Polzberg palaeobiota: Elpistoichthys, Gigantopterus, Saurichthys, Thoracopterus, Habroichthys, Nannolepis, and Peltopleurus
Summary
Palaeobiota of fossiliferous sites known as Konservat-Lagerstätte[1] (see a lso2,3) are precious sources of palaeobiological information[4]. The locality, situated in Lower Austria (Fig. 1A) and known as Schindelberg or Pölzberg[11,12] in historic collections, appears with lower Carnian Reingraben Shales (“Reingrabner Schiefer”, “Trachyceras Schiefer”). The biostratigraphic data hint to a Julian 2 Ib (Austrotrachyceras austriacum Zone, A. minor biohorizon) age of the main fossiliferous part of the Polzberg section These important palaeontological findings highlight the importance and special position within the Upper Triassic Carnian Pluvial Episode (CPE19,20) and the food web with its food chains of the Polzberg Konservat-Lagerstätte. The entirety of the fossil taxa found so far provides new insights into the Upper Triassic (lower Carnian) trophic web and food chains of the Polzberg palaeobiota. Due to the soft nature of the marly deposits, the entire area encompassing the Reingraben Shales is brownish and weathered down to few metres at the surface, which requires mines or fresh, undisturbed outcrops at the nearby stream
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