Mosasaurid and plesiosaurian remains from marginal facies of the lower Campanian (Upper Cretaceous) Bottrop and Vaals formations of western Germany

Isolated remains of mosasaurids and plesiosaurians are recorded from the lower Campanian Bottrop and Vaals formations of North Rhine-Westphalia, western Germany. A tooth crown from Bottrop-Fuhlenbrock, referred to an elasmosaurid plesiosaurian, represents the first record of this group from late-Upper Cretaceous strata of the area. Another presumed plesiosaurian remain is a fragmentary gastralium from Duisburg-Walsum. Some of the mosasaurid material from the Bottrop Formation (a tooth crown and a vertebra from Duisburg-Walsum and Bottrop-Fuhlenbrock) is assigned to the subfamily Plioplatecarpinae. The Vaals Formation, which is a lateral equivalent of the Bottrop Formation, yielded a single tooth crown, found at Aachen-Bildchen, that is here referred to the genus Hainosaurus. These finds from the Bottrop and Vaals formations constitute evidence for the presence of mosasaurids and plesiosaurians in proximal shelf to nearshore settings during the Campanian. The mosasaurid occurrences in particular may be an indicator that diversity and abundance increased in more basinward facies and a greater palaeowaterdepth.