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

在晚古生代和中生代陆相沉积中有大量的鲨鱼遗骸。这些鱼类的古生态学要么作为永久的淡水居民，要么作为季节性迁移到淡水环境产卵的溯河动物进行讨论。本项目以二叠纪-石炭世和晚三叠世的淡水鲨鱼化石Lissodus和Orthacanthus为研究对象，利用稳定同位素对其牙齿和脊椎的地球化学档案进行研究。骨骼磷灰石的氧同位素组成反映了牙齿矿化时的环境水化学，指示了淡水或海水环境。此外，淡水同位素信号还可用于评估含鲨湖泊的相对高度，以确定造山带及其盆地的古地形和排水模式。此外，淡水鲨鱼的时空分布将通过可能相关的卵囊的出现进行严格评估。新的淡水-鲨鱼源氧同位素数据集将为晚古生代和早中生代的大气水和水文同位素组成提供新的认识。

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.