The first description of Halisaurus (Reptilia Mosasauridae) from Europe, from the Upper Cretaceous of Belgium

This study represents the first extensive description of the skull of species of the genus Halisaurus Marsh 1869. Halisaurus ortliebi (= Phosphorosaurus ortliebi of Dollo, 1889), from the Maastrichtian of Belgium, shows, several character states, including a unique ventral fossa of the parietal. Comparisons are made with the North American H. platyspondylus . H. Sternbergi (Wiman, 1920) is no longer considered as belonging to the genus Halisaurus .