Paleogene

Part of speech: noun, adjective

Definitions

1. A major division of geological time that follows the Mesozoic era and is characterized by the rise of mammals and birds after the dinosaurs' extinction
2. The first of the two epochs in the Cenozoic era, marked by significant environmental changes and the diversification of life forms on Earth
3. A period in Earth's history, extending from about 66 million to 23 million years ago, notable for the development of modern ecosystems and climate transitions

Etymology: "Paleogene" is a technical coinage, built in the modern scientific era from two Ancient Greek elements. "Palaiós" meant "old," and "geneá" meant "generation" or "birth," and the second element survives in English words such as "genesis" and "gene." Combined with the suffix "-gene," the result describes the oldest part of the recent geological record, the stretch of time that opened once the dinosaurs had disappeared. The name was not something the ancient Greeks could have used, since the word was assembled by geologists long after classical times to label a specific slice of Earth's history. Its prefix "paleo-" is the same one found in "paleontology" and "Paleolithic," and it appears in many scientific compounds where it signals ancient or early forms of life or rock. The "-gene" element works the same way in terms like "Neogene," the period that follows, so the two names form a matched pair.