Short answers, pulled from the story.
The Cretaceous period lasted from about 143.1 million years ago to 66 million years ago, spanning approximately 77.1 million years. It is the third and final period of the Mesozoic Era and the longest geological period of the entire Phanerozoic.
The name derives from the Latin word creta, meaning chalk. Belgian geologist Jean d'Omalius d'Halloy coined the term Terrain Cretace in 1822, drawing on the extensive chalk beds found in the upper Cretaceous strata of Western Europe, including those that form the white cliffs of Dover. Chalk consists of microscopically small calcite skeletons of coccolithophore algae that accumulated on ancient seafloors.
The Cretaceous ended with a large mass extinction widely attributed to the impact of an asteroid that formed the Chicxulub crater, whose boundaries encompass parts of the Yucatan Peninsula and extend into the Gulf of Mexico. A global iridium-rich layer associated with the crater has been dated at 66.043 million years ago. The extinction eliminated three-quarters of Earth's plant and animal species, including non-avian dinosaurs, pterosaurs, and large marine reptiles.
The Cretaceous reached extreme warmth during the Mid-Cretaceous Hothouse, which lasted from the early Albian until the early Campanian. Mean annual polar temperatures exceeded 14 degrees Celsius, and tropical sea surface temperatures during the Cenomanian-Turonian Thermal Maximum reached at least 30 degrees Celsius. Deep ocean temperatures were estimated between 12 and 20 degrees Celsius, far above modern values.
The earliest widely accepted fossil evidence of flowering plants consists of monosulcate pollen grains from the late Valanginian, around 134 million years ago, found in Israel and Italy. Flowering plants underwent rapid diversification through the middle Cretaceous and became the dominant group of land plants by the end of the period.
Omnivores, insectivores, and scavengers were the primary survivors. Mammals and birds that made it through fed on insects, larvae, worms, and snails that in turn depended on dead organic matter. Crocodilians survived because they were semiaquatic, could scavenge, and could endure months without food. Sea turtles of the family Cheloniidae also survived; one lineage is today represented solely by the leatherback sea turtle.