The Lancian portion of the Javalina formation, inside Big Bend national park, Texas. 66 million years ago. During this time, the western interior seaway split North America down the middle into two sub continents. Appalachia on the East and Laramidia to West. Everything in between was submerged. This is why we have so many fossils of aquatic animals such as sharks, bony fish, crustaceans, mollusks and marine reptiles in what is now middle-America. In west Texas, one of the largest animals to ever fly under its own power was discovered, quetzalcoatlus. Pterosaurs at the end of the Cretaceous had become a diverse clade branching out into wide variety of unique feeding specializations. And then you had the azhdarchid family, to which quetzalcoatlus belonged, which had become massive. They were large enough to prey on smaller dinosaurs, spearing them from above like a stork, or detect carrion from the sky miles away.
Depicted here are two quetzalcoatlus squabbling over the beached remains of a mosasaurus. An aquatic lizard closely related to monitors and snakes that had evolved to inhabit in the ocean like a whale.