We report the discovery of a new species of marine reptile, a mosasaur, from the Upper Cretaceous (Maastrichtian) of The Netherlands. Prognathodon saturator sp. nov. is represented by an almost complete skull and much of the postcranial skeleton, and is one of the largest mosasaurs discovered to date. The stout skull and extremely massive jaws are more powerfully built than in any other known mosasaur. Bite marks, the partial disarticulation and scattering of the skeleton, and the presence of associated teeth of Squalicorax and Plicatoscyllium suggest extensive scavenging by sharks.

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Birds known from more than isolated skeletal elements are rare in the fossil record, especially from the European Mesozoic. This paucity has hindered interpretations of avian evolution immediately prior to, and in the aftermath of, the Cretaceous-Tertiary (K-T) extinction event. We report on a specimen of a large ornithurine bird (closely related to Ichthyornis) from the uppermost Cretaceous (Maastricht Formation) of Belgium. This is the first record of a bird from these historic strata and the only phylogenetically informative ornithurine to be recovered from the Mesozoic of Europe. Because this new specimen was collected from 40 m below the K-T boundary (approximate age of 65.8 Ma), it is also the youngest non-neornithine (= non-modern) bird known from anywhere in the world.

Co-ossified pygal and caudal vertebrae in Late Cretaceous mosasaurs from the southeast Netherlands, northeast Belgium, and North America are compared with lumbar and caudal vertebrae from fossil and extant whales. Both infectious spondylitis and idiopathic vertebral hyperostosis afflicted these marine tetrapods. The causes of the infectious disease and of the idiopathic disease are similar in the compared life forms. The location of idiopathic hyperostosis along the vertebral column implicates axial locomotion in mosasaurs, as in whales.

From Upper Campanian turbiditic marls at Beckum in the Munster Basin (NW Germany) the anterior portion of a mosasaurid premaxilla with abutting fragments of the left and right maxilla is described and referred to the genus Clidastes. It shows the process of tooth replacement very well. This taxon is recorded for the first time from Germany. Clidastes co-existed in central Europe with other mosasaurids such as representatives of the genus Leiodon and Mosasauridae indet.

Remains of elasmosaurid plesiosaurs are exceedingly rare in the type-Maastrichtian strata (Late Cretaceous, southeast Netherlands and northeast Belgium), in stark contrast to relatively common skeletal remains of mosasaurs. Here, we present an analysis of δ13C stable isotope values for tooth enamel of two elasmosaur teeth from the type Maastrichtian. The δ13C signal is a proxy for foraging area, trophic level and diving behaviour, the net value of which in these rare elasmosaurs turns out to be not noticeably different from that for the much commoner mosasaurs in the type Maastrichtian. Therefore, the rarity of elasmosaurs in the area probably reflects a primary near-absence of such reptiles during the latest Cretaceous, rather than a taphonomic artefact