Palaeoecology and migration behaviour of the Palaeozoic to Mesozoic freshwater sharks Lissodus and Orthacanthus using stable isotopes

点击翻译按钮获取中文摘要

Shark remains are abundant in Late Palaeozoic and Mesozoic continental deposits. The palaeoecology of these fishes is discussed either as permanent freshwater residents or as anadromous animals, which seasonally migrated into freshwater environments for spawning. The aim of this project is the investigation of the geochemical archive of teeth and spines of the fossil freshwater sharks Lissodus and Orthacanthus based on two case studies from the Permo-Carboniferous and the Late Triassic using stable isotopes. The oxygen isotopic composition of skeletal apatite reflects the ambient water chemistry at the time of tooth mineralisation being indicative for a fresh- or seawater environment. Furthermore, freshwater isotopic signals allow the evaluation of the relative altitude of shark-bearing lakes in order to specify the palaeotopography and drainage pattern of orogenic belts and their basins. In addition, the spatial and temporal distribution of freshwater sharks will be critically assessed by the occurrences of possibly related egg capsules. The new freshwater-shark-derived oxygen isotope data set will provide new insights about the isotopic composition of meteoric waters and the hydrology in Late Palaeozoic and Early Mesozoic times.