1. Dinosaurs (excluding birds): Dinosaurs, except for the avian lineage leading to modern birds, became extinct at the end of the Cretaceous period, which marks the beginning of the Cenozoic era.
2. Ammonites: Ammonites, a group of marine cephalopods, also went extinct at the end of the Cretaceous period.
3. Mosasaurs: Mosasaurs, large marine lizards that resembled modern-day monitor lizards, were another group that became extinct at the end of the Cretaceous.
4. Plesiosaurs: Plesiosaurs, marine reptiles with long necks and flippers, were part of the marine megafauna that disappeared during the Cretaceous-Paleogene extinction event.
5. Ichthyosaurs: Ichthyosaurs, marine reptiles resembling modern-day dolphins, similarly became extinct at the end of the Cretaceous period.
6. Pterosaurs: Pterosaurs, flying reptiles that included pterodactyls and other gliding or flapping forms, were among the casualties of the Cretaceous-Paleogene extinction event.
7. Trilobites: Trilobites, an ancient group of marine arthropods, had already become extinct by the end of the Paleozoic era, long before the Cenozoic period began.