Discovery of a new species of mosasaur, Thalassotitan atrox, a giant predator from the Upper Cretaceous

Thalassotitan atrox lived in the Upper Cretaceous, 67 million years ago, when the Atlantic Ocean covered part of Morocco with a shallow sea. The mosasaurs of the Moroccan phosphates were very diverse, with specimens adapted to catch fish and squid, others exclusively piscivorous, or still others that fed on animals with shells (such as ammonites). In this rich ecosystem, a species was at the top of the food chain: Thalassotitan atrox. It was a mosasaur with a short, wide snout and massive, conical teeth, like those of modern killer whales. Imposing, this mega-predator had an enormous skull of 1.4 meters and a body measuring nearly 12 meters long. An aspect that explains its name, from the Greek Thalassa (sea), titan, (giant) and atrox, (cruel, merciless).

The jaws and teeth of this large marine lizard were used to seize and shred large prey, unlike most mosasaurs which had long jaws to catch prey of modest size. Based on the shape and condition of the broken and worn teeth of Thalassotitan atrox, its diet must have consisted of large fish and other vertebrates, the carcasses of which greatly damaged its teeth. In addition, numerous fossil remains of acid-damaged marine vertebrates, probably from the digestion of a predator, have been found in the same sedimentary layers as Thalassotitan atrox. Among these fossils considered to be the food remains of this new species of marine reptile are large fish, a sea turtle, the remains of a half-meter long plesiosaur head, and the jaws of at least three different species of small mosasaurs.

The discovery of Thalassotitan in the marine sediments of the Moroccan phosphates once again confirms the very important specific and ecological diversity of mosasaurs. They offer a better understanding of marine ecosystems just before the great mass extinction of the Cretaceous-Tertiary transition, which represents the last of the major biotic crises in the history of the biosphere.

• Référence : Nicholas R. Longrich, Nour-Eddine Jalil, Fatima Khaldoune, Oussama Khadiri Yazami, Xabier Pereda-Suberbiola, Nathalie Bardet. Thalassotitan atrox, a giant predatory mosasaurid (Squamata) from the Upper Maastrichtian Phosphates of Morocco, Cretaceous Research, 2022, https://doi.org/10.1016/j.cretres.2022.105315.

• Lire l'article : Thalassotitan atrox, a giant predatory mosasaurid (Squamata) from the Upper Maastrichtian Phosphates of Morocco