The Marine Pachypleurosaur Serpianosaurus Germanicus Nov. Spec. – Skeleton and Isolated Bone Remains from the Pelsonian (middle Triassic) of the European Germanic Basin Carbonate Intertidals and Its Paleobiology and Taphonomy

The large marine pachypleurosaur sauropterygian Serpianosaurus germanicus nov. spec., representing the oldest well known record of this genus from the Pelsonian, is introduced based on a postcranial skeleton. Of younger age are the Serpianosaurus mirigolensis (Rieppel, 1989) specimens from the Illyrian/Fassanian boundary (Grenzbitumen Bed) of the northwestern Tethys (Monte San Giorgio). Additional materials from Germany contain individual remains of different sexes and ages, all of which have been found in shallow marine to intertidal carbonate deposits. The postcranial skeleton and single bone remains from the Karlstadt Formation (upper Pelsonian, Anisian) of the Middle Triassic from different German sites demonstrate that this genus is more common in the Germanic Basin, but also is present in the northern Tethys. The paleogeography and facies distribution indicate evaporative to shallow marine conditions with extensive intertidal flats and sabkhas on the southern Germanic Basin coasts at that time. One possible reason for the abundance of Serpianosaurus during late Pelsonian time is a food chain that was based on horseshoe crabs, the eggs of which might have been a main target for the fish that were the primary food source for the pachypleurosaurs. Serpianosaurus and other marine vertebrates may have been killed by storm events and their carcasses deposited on intertidal flats where they were themselves food sources for large carnivorous thecodont archosaurs such as Ticinosuchus (Chirotherium tracks), or ?Arizonasaurus (Isochirotherium tracks), the footprints of which occur on the intertidals where Serpianosaurus and other marine vertebrate remains were deposited.