Upper Jurassic tidal flat megatracksites of Germany—coastal dinosaur migration highways between European islands, and a review of the dinosaur footprints

Abstract

Dinosaur tracks occur at three vertebrate tracksites in north-western Germany, in the acanthicum/mutabilis ammonoid biozone of the basal Upper Kimmeridgian (Upper Jurassic, KIM 3-4 cycle, 152.70-152.10 Ma). The trackbeds are mud-cracked, siliciclastic, tidal sand flat biolaminates, overlain by paleosol beds. Channels contain rare fossils of sauropod, ornithopod and pterosaur bones as well as shark and plant remains. Large sauropod tracks of the Elephantopoides type, which have been found in an intertidal megatracksite environment to the north of the Rhenish Massif, are reviewed herein, together with a camptosaurid track type (?Iguanodontipus), the theropod track Megalosauropus and possible dryosaurid Grallator tracks. These large dinosaur tracks have been reviewed and compared to all other known European localities. At the Barkhausen tracksite with its important ichnoholotypes, trackways of a possible sauropod herd consisting of ten small to medium-sized individuals and one large individual have been exposed, revealing different speeds of travel as well as important social behaviour in these large herbivorous dinosaurs. Two theropods also left their imprints on the same track horizon, one travelling towards the south in a direction contrary to the movement of the herd, and the second travelling towards the north-west, cutting across the other trackways. Five different types of Upper Jurassic dinosaur tracks have now been recorded from coastal environments scattered around Europe, with the best footprint records forming extensive megatracksites in biolaminates between Jurassic islands in central Europe. These intertidal flats formed periodic bridges between the islands, allowing dinosaur interchanges and migrations between America and Eurasia, which may help to explain the much broader palaeobiogeographic distributions of dinosaur species during the Late Jurassic.