The Middle Triassic vertebrate deposits of Kupferzell (Germany) : Palaeoenvironmental evolution of complex ecosystems

In 1977, within 3 months of excavation, a 500 m spanning road-cut near Kupferzell (southern Germany) produced a total of ~30,000 vertebrate remains from the Middle Triassic Lower Keuper. The bulk of the material stems from two temnospondyl amphibians, Gerrothorax pulcherrimus (~70%) and Mastodonsaurus giganteus (~30%), with the pseudosuchian archosaur Batrachotomus kupferzellensis ranging first among the other remains. Analyses of data collected during excavation, supplemented by new fieldwork, provide rich information on the sedimentary setting as well as the development of the fauna and their ecosystems. The sequence consists of: basal coaly mudstones (K1), massive siltstones (K2), green siliciclastic mudstones (K3), yellow to pale brown marlstones (K4), and yellow massive dolostones (K5). The deposits comprise a succession of similar water bodies that were emplaced on a lacustrine to floodplain setting in which carbonate muds dominated. Two main lake systems, with intermittent/periodical marine influence, as well as relatively stark periods of drought, harboured complex vertebrate ecosystems. These were dominated by a relatively high diversity of fishes and temnospondyl amphibians with a lesser, but notable, presence of archosaurs, forming the top predators of the trophic web. The sequence records alternating periods of flooding and desiccation, shaping a relatively complex environmental setting that was likely prone to the presence of life, eventually becoming an exceptional fossil lagerstätte. Kupferzell, together with nearby contemporaneous localities, represent relatively diverse and complex ecosystems (including several top predators) that allow understanding the evolution and palaeoecology of Middle Triassic vertebrate communities, including the groups that diversified during the Mesozoic era