The Lower Keuper (Erfurt Formation, Middle Triassic) fossillagerstätten from SW Germany: flourishing tetrapod ecosystems

Even if the knowledge of Triassic tetrapod communities and their role in terrestrial ecosystems has increased in the recent decades, the paucity of fossil sites from this time interval has hindered their complete understanding. In order to shed light on how the Triassic tetrapod communities were, evolved and interacted in their habitats, we are carrying out a series of multidisciplinary studies on the Ladinian Lower Keuper successions (Erfurt Formation) of southwestern Germany. These facies were deposited in a vast epicontinental platform of the Central European Basin, influenced by the Tethys Sea. The Lower Keuper in the study areas consists of a 20–25 m thick succession of alternating siliciclastic and carbonate deposits, mostly grey to green mudstones and marlstones, and yellowish to blueish dolostones, as well as occasional sandstones. The succession is divided in more discrete units, some of which forming exceptional fossillagerstätten with thousands of tetrapod remains recovered and tens of new tetrapod taxa (including basal members of different lineages) described to date. Sedimentological, taphonomic and palaeoecological data show that ecosystems were complex, with several levels within the trophic chain and including at least two top predators: a pseudosuchian archosaur and a giant capitosaur temnospondyl. Of note, fish diversity is particularly high, with at least 14 taxa so far known. The occurrence of the same vertebrate taxa, but in different proportions and from different ontogenetic stages throughout the stratigraphic succession and in different localities corresponding to slightly different environmental settings, indicates stability of the ecosystems.