Open Geosciences (Nov 2015)
The vertebrates from the Lower Ladinian (Middle Triassic)bonebed of Lamerden (Germany) as palaeoenvironmentindicators in the Germanic Basin
Abstract
A marine/limnic vertebrate fauna is describedfrom the enodis/posseckeri Bonebed mixed in a bivalveshell-rich bioclastic carbonate rudstone at the easterncoastal margin of the Rhenish Massif mainland at Lamerden(Germany) within the western Germanic Basin (CentralEurope). The condensation layer is of Fassanian (Ladinian,Middle Triassic) in age. The vertebrate biodiversityincludes five different shark, and several actinopterygianfish species represented by teeth and scales. Abundantisolated bones from a small- and a large-sized pachypleurosaurNeusticosaurus species, which can be composedas incomplete skeletons, originate from dense populationsof different individual age stages. Important faciesindicator reptiles are from the thalattosaur Blezingeriaichthyospondyla which postcranial skeleton is reconstructedhypothetically using additional postcranialbones from similar aged various German localities. Thevertebrate biodiversity of the enodis/posseckeri bonebedof Lamerden reflect a limnic/fluvial freshwater influencedfauna (amphibians/terrestrial and marine reptiles) withdominance of normal saline marine influences. Macroalgaemeadow adapted placodont reptiles are absent inLamerden, as well as open marine-adapted ichthyosaurs,supporting a lagoon with fresh water influence position atthe Rhenish Massif mainland coast. In those contemporanousbrackish lagoons, which seem to be isochronousto northern Tethys lagoons of the Kalschieferzone at theMonte San Giorgio (Switzerland/Italy), small pachypleurosaurswere abundant prey in both regions for reptilepredators, especially large paraxial swimming alligatorhabitus-like Paranothosaurus, which even contain stomachcontents of pachypleurosaurs.
Keywords
