Bromalites from the Upper Triassic Polzberg section (Austria); insights into trophic interactions and food chains of the Polzberg palaeobiota

Alexander Lukeneder,Robert Niedźwiedzki,Dawid Surmik,Mariusz A Salamon,Tomasz Brachaniec,Przemysław Gorzelak

doi:10.1038/s41598-020-77017-x

Abstract

A rich assemblage of various types of bromalites from the lower Carnian “Konservat-Lagerstätte” from the Reingraben Shales in Polzberg (Northern Calcareous Alps, Lower Austria) is described for the first time in detail. They comprise large regurgitalites consisting of numerous entire shells of ammonoid Austrotrachyceras or their fragments and rare teuthid arm hooks, and buccal cartilage of Phragmoteuthis. Small coprolites composed mainly of fish remains were also found. The size, shape and co-occurrence with vertebrate skeletal remains imply that regurgitalites were likely produced by large durophagous fish (most likely by cartilaginous fish Acrodus). Coprolites, in turn, were likely produced by medium-sized piscivorous actinopterygians. Our findings are consistent with other lines of evidence suggesting that durophagous predation has been intense during the Triassic and that the so-called Mesozoic marine revolution has already started in the early Mesozoic.

Highlights

Bromalites, the fossilized products of digestion, are precious source of palaeobiological information[1,2,3,4]
We report fossilized vomits and coprolites, which provide new insights into pelagic invertebrates-vertebrates trophic chain of the Late Triassic Polzberg biota
We argue that a durophagous shark Acrodus was likely a producer of regurgitalites studied, other durophagous predators, which were present in the latest Ladinian and early Carnian in the other areas of the east part of Alpine domain, including durophagous and semi-durophagous reptiles (recorded in a few outcrops in NE Italy64,65; Slovenia[66]; Hungary (Bakony)[64], some hybodontid sharks (e.g., Palaeobates, Asteracanthus; see[64,67] and some actinopterygian fishes (e.g., Colobodus64,67), cannot be fully excluded

Summary

Introduction

Bromalites, the fossilized products of digestion, are precious source of palaeobiological information[1,2,3,4]. A detailed study on bromalites from Northern Calcareous Alps has been lacking They have been only briefly mentioned by Glaessner[11] from the Upper Triassic Polzberg locality (the Northern Calcareous Alps). This locality ( known as Pölzberg[12]; southern part of the Lunz Nappe, Lower Austria; Fig. 1) comprises the lower Carnian Reingraben Shales which form at this locality a fossiliferous site known as “Konservat Lagerstätte” sensu Seilacher[13] (see [14,15]). Excavation campaigns were organized by the Austrian Geological Survey in 1885 and 1909 During these years, two fossil mines were driven into the basal part of the Reingraben Shales yielding better-preserved fossils, not harmed by weathering of soft marly deposits on the surface. Within the Lunz Nappe in Lower Austria, the Reifling basin is located between the Polzberg and Großreifling

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Conclusion