Flock of Hesperornis on rocky cliffs by GabiPaleo on DeviantArt (original) (raw)

Hesperornis - a large aquatic bird from the Late Cretaceous. These slender birds barely had any wings and likely led a lifestyle similar to that of modern penguins or cormorants.
Unlike modern birds, Hesperornis had actual teeth, a feature that was becoming uncommon by the Late Cretaceous and completely vanished after the K-Pg extinction. However, some modern birds possess pseudoteeth, appearing as sharp structures on their tongues or beaks.
Despite the presence of many predators and potential rivals (like Pteranodon, Ichthyornis, and various sea reptiles), Hesperornis thrived in its environment, due to adaptations such as lobed toes, similar to those of modern grebes, which made it a proficient swimmer.