premise: In the Cretaceous non-avian dinosaurs died out all in one morning.
hypothesis: Cretaceous . The Cretaceous ended with a large mass extinction , the Cretaceous -- Paleogene extinction event , in which many groups , including non-avian dinosaurs , pterosaurs and large marine reptiles died out . Edmontosaurus ( [ ɛdˌmɒntəˈsɔːrəs ] ) is a genus of hadrosaurid ( duck-billed ) dinosaur . Tyrannosaurus ( [ tᵻˌrænəˈsɔːrəs , _ taɪ - ] , meaning `` tyrant lizard '' , from the Ancient Greek tyrannos , `` tyrant '' , and sauros , `` lizard '' ) is a genus of coelurosaurian theropod dinosaur .