A 2.5-meter-long mosasaur, named Garamaudo bauciensis, lived in a lake near Aix-en-Provence about 84 million years ago, according to a study published on September 28, 2026, in PCI Paleontology by CNRS paleontologists Nathalie Bardet and Alexandra Houssaye. This discovery is significant because it challenges previous assumptions that all mosasaurs were strictly marine predators. Earlier research had suggested that these ancient reptiles, which could grow up to 15 meters in length, lived exclusively in the open ocean. The fossil remains of Garamaudo bauciensis were discovered in 1997 on an outcrop called Bouc-Bel-Air in the Bouches-du-Rhône region. The collection includes about 20 pieces, such as a left jaw, nine vertebrae, six ribs, a humerus, and a half-pelvis. A single vertebra found 20 meters away in 2018 suggests the presence of at least two individuals. The sediments surrounding the fossils indicate they date to the Santonian period, around 84 million years ago. The humerus of Garamaudo bauciensis is long and slender, unlike the powerful swimming fins of other mosasaurs. Its pelvis remains fused, with the ilium pointing backward, a feature seen in terrestrial lizards. High-resolution scans of the dense bones, conducted in Montpellier, suggest the animal was adapted to stay buoyant in water without using much energy. This adaptation would have limited its acceleration, leading researchers to propose that it hunted by ambush, moving like an eel rather than using tail movement. The dense bones also suggest that the mosasaur would have been prone to fractures if it attempted to walk on land. The vascularization of the bones indicates a growth rate that is more vigorous than in modern lizards but less than in marine mosasaurs. This suggests that Garamaudo bauciensis never left the shallow waters of the nearby lake basin. The lake basin of Bouc-Bel-Air also yielded other fossils, including freshwater mollusk shells, an alligator gar of the genus Atractosteus, and a coelacanth, Axelrodichthys megadromos. A turtle and small crocodilians complete the fauna, with no large crocodiles present. Paleontologists have identified two other freshwater mosasaurs: Pannoniasaurus in Hungary and a specimen from Villeveyrac in the Hérault. These all belong to the same subfamily, the tethysaurines, the only branch of the group to have colonized lakes and rivers. The Museum of Natural History in Aix-en-Provence currently preserves the bones of Bouc-Bel-Air.