Choristodera

Choristodera is an extinct order of marine diapsid reptiles that lived from the Early Jurassic to the Late Cretaceous epochs. These reptiles were diverse, inhabiting both freshwater and marine environments across what is now Eurasia and North America. While their exact phylogenetic placement has been debated, they are generally considered to be within the larger group Archosauromorpha, though their relationship to modern archosaurs like crocodiles and birds is distant.

Fossils of choristoderes exhibit a range of adaptations. Some species were small and elongated, resembling modern lizards, while others were larger and more robust, with adaptations for aquatic life. Many possessed long, crocodile-like snouts, and some had specialized teeth for grasping fish, their primary prey. Their skeletal features, such as the arrangement of their skull bones and the structure of their limbs, provide clues to their lifestyle and evolutionary history.

The group includes several notable genera, such as Champsosaurus, a long-snouted predator found in North America, and Monjurosuchus from Asia. The fossil record indicates a gradual diversification of choristoderes throughout the Mesozoic Era. Their extinction at the end of the Cretaceous, likely due to environmental changes associated with the K-Pg extinction event, marks the end of this unique lineage of reptiles.