The Consthum Lagerstätte (Luxembourg) – a window into the palaeoecology of Early Devonian marine-terrestrial transitional facies

Abstract In the Rhenish Massif, a vast Lower Devonian deltaic system along the southern edge of Laurussia (Old Red Continent) continues to yield exceptional fossils from marginal marine to terrestrial transitional facies. Hitherto, these occurrences are mainly known from the lower Moselle and West-Eifel regions in Germany. Here, we introduce a new Lagerstätte situated in northern Luxembourg, which extends the known geographical occurrence of this important biota further to the west. It agrees more-or-less with previously known localities from Germany in the general composition of the fossil association, which is composed of a bivalve-lingulid-arthropod-dominated association with a few associated vertebrate remains, macroplants, and some miospores. Unique features include a mass occurrence of clam shrimp, the high abundance of scorpions and juvenile specimens of the eurypterid Adelophthalmus as well as the occurrence of supposed euthycarcinoids and (stem?) onychophorans. Analyses of the Consthum Lagerstätten and biota have great potential to further illuminate the palaeoecology and palaeogeography of marginal-marine to terrestrial transitional settings in the Ardenno-Rhenish Lower Devonian and to decipher the palaeoecological origin of various lineages of organisms, such as clam shrimp, scorpions, and onychophorans. This is of paramount importance for a holistic understanding of the biology and physiology of their modern descendants.