A new species of Halisaurus (Mosasauridae: Halisaurinae) from the lower Maastrichtian (Upper Cretaceous) of the Western Desert, Egypt

Mosasaurids were highly diverse and dominant as predators in late Cretaceous marine ecosystems. In the Maastrichtian, the Halisaurinae, a clade of relatively small-bodied mosasaurids, became common, especially in North Africa. Here, we report a new species of halisaurine from the lower Maastrichtian Dakhla Shale of the Western Desert of Egypt. Halisaurus hebae sp. nov. resembles Halisaurus platyspondylus and H. arambourgi in the shape of the frontal, suggesting close affinity with those species. A revised halisaurine phylogeny shows a cluster of species characterized by modification of the orbital bones to accommodate large eyes, suggesting a shift towards the use of visual cues to find prey, perhaps in low light conditions. The abundance and diversity of halisaurines in Africa contrasts with their relative rarity elsewhere in the world, emphasizing the regionalization of marine reptile faunas in the Maastrichtian.