Taphonomy of fish concentrations from the Upper Jurassic Solnhofen Plattenkalk of Southern Germany
Pan, Yanhong; Fürsich, Franz T.; Chellouche, Patrick; Hu, Liang
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen Band 292 Heft 1 (2019), p. 73 - 92
96 references
published: Apr 23, 2019
manuscript accepted: Jan 2, 2019
manuscript received: Dec 18, 2018
ArtNo. ESP155029201003, Price: 29.00 €
Abstract
The density of vertebrate fossils on bedding planes is generally very low in the Upper Jurassic plattenkalks forming the Solnhofen fossil Lagerstätte. There are, however, a few bedding planes where large concentrations of the small fish Leptolepides sprattiformis (Blainville, 1818) occur. The aim of this paper is to analyse and interpret these fish concentrations from a taphonomic point of view. For this purpose, the taphonomic features of L. sprattiformis concentrations on three large slabs were semi-quantitatively analysed. The concentrations of individuals on bedding planes are explained as recording local mass mortality events caused by tropical storms that, for short intervals, disrupted the pycnocline which separated hypersaline, oxygen-poor to anoxic bottom waters from normal marine surface waters in the Plattenkalk basins. Mass mortality is supported by tetany features such as gaping jaws, hyperextended branchiostegal rays, and splayed fins, which occur in the majority of the specimens. The generally excellent preservation of the fish resulted from lack of post-mortem floatation, rapid burial and/or overgrowth by microbial films, and quick re-establishment of the pycnocline with inhospitable conditions on the basin floor. The post-mortem concave-arching of the backbones and various displacements of the vertebral column were most likely caused by varying decay resistance of soft tissues and the pressure of decay gases in the body cavities, respectively. The taphonomic analysis of fish concentrations can provide very detailed palaeoenvironmental information and serves as an independent line of evidence for palaeoenvironmental reconstructions that complements geochemical and sedimentary data.
Keywords
Leptolepides sprattiformis
•
concave-arching backbones •
taphonomy •
palaeoenvironment •
Plattenkalk •
fossil Lagerstätte •
Tithonian