Mosasaurus Prognathodon anceps tooth in Matrix Fossil

Prognathodon, also known as “Forejaw tooth,” is a carnivorous reptile that lived during the Campanian to Maastrichtian stages of the Cretaceous period. It is classified as a mosasaur, a group of marine lizards that were apex predators in the Late Cretaceous. However, Prognathodon specialized in feeding on tough-shelled prey such as shellfish, ammonites, and turtles, similar to basal placodont reptiles from the Triassic period.

Prognathodon’s size varied depending on the species, ranging from 6 to just under 14 meters in length. Fossil locations indicate that it had a worldwide distribution, but it is particularly well-known in Europe and North America.

The reptile had a robust and heavy jaw that could withstand a high bite force, supplied by powerful jaw muscles. Its teeth were strong and well-adapted for crushing, with serrations that allowed them to destroy protective shells and shear flesh. Prognathodon also had bony rings around its eye sockets, which helped its eyes withstand the higher water pressure of deep water when diving for ammonites.

Two discoveries in Canada in the early 21st century revealed Prognathodon’s full body shape and diet. One specimen contained turtle and ammonite fossils in its stomach, along with a 160 cm long fish, indicating that while Prognathodon was a specialized predator, it was also opportunistic in its feeding.

The reason why Prognathodon shifted towards this type of diet remains uncertain. It could have been due to competition for the apex predator niche or a decline in the number of large prey animals that mosasaurs typically fed on. Alternatively, Prognathodon may have simply exploited an abundant food source. Globidens, another mosasaur, also adjusted to this type of diet and had particularly large and rounded crushing teeth in its mouth.