New data on the marine Upper Triassic palaeobiota from the Polzberg Konservat-Lagerstätte in Austria

Abstract

Here we report new data on the Upper Triassic Polzberg Konservat-Lagerstätte in the Northern Calcarous Alps of Lower Austria. We examined new fossil material obtained from bed-by-bed collections of the well-laminated Reingraben Shales. Over 5290 new fossils of various marine taxa were collected within the fossiliferous layers from the Early Carnian (Julian 2 Ib, Austrotrachyceras austriacum Zone). The newly collected assemblage comprises ammonoids (Austrotrachyceras, Paratrachyceras, Carnites, Simonyceras), belemnoids (Phragmoteuthis, Lunzoteuthis), bivalves (Halobia, div. indet taxa), gastropods (caenogastropods/heterobranchs), thylacocephalan arthropods (Austriocaris, Atropicaris), crustaceans (the decapod Platychela and isopods Obtusotelson, Discosalaputium), branchiopods (Euestheria), polychaetes (Palaeoaphrodite sp. and an unidentified eunicid polychaete), acytinopterygians (Saurichthys, Polzbergia, Peltopleurus, Habroichthys), cartilaginous fishes (Acrodus), coelacanth fish (“Coelacanthus”), a lungfish (Tellerodus), and numerous conodont clusters (Mosherella). Bromalites (coprolites and regurgitalites) produced by piscivorous actinopterygians and durophagous fish accompany the Polzberg palaeobiota along with rare plant remains (Voltzia, div. indet plants). Based on new findings the palaeobiota characterises an intermittent colonisation by abundant benthic halobiid bivalves and a predator-dominated (fish, belemnoids) nektic community. The prerequisites for high-quality preservation—calm and oxygen-depleted conditions—prevailed at the sea floor of the Polzberg Konservat-Lagerstätte. Normal marine conditions prevail in the Reifling Basin, occasionally interrupted by freshwater influx. New in situ findings of benthic and nektic taxa highlight the great value of the unique Polzberg palaeobiota and the autochthonous deposition of the inhabitants within the palaeohabitat. The fauna and flora from the Polzberg Konservat-Lagerstätte, deposited during the Carnian Pluvial Episode or Carnian Wet Intermezzo, points to a carbonate platform decline followed by the deposition of laminated deposits in warmer and wetter conditions.