Across
- 4. an animal lacking a backbone, such as an arthropod, mollusk, annelid, coelenterate, etc
- 5. an expert in or student of geology.
- 7. a massive supercontinent that existed approximately 250 million years ago, composed of all the present-day continents joined together.
- 10. the action or process of classifying something according to shared qualities or characteristics.
Down
- 1. an animal of a large group distinguished by the possession of a backbone or spinal column, including mammals, birds, reptiles, amphibians, and fishes.
- 2. a length or porion of time
- 3. a person who studies or is an expert in the branch of science concerned with fossil animals and plants.
- 6. a major division of time that is a subdivision of an eon and is itself subdivided into periods.
- 8. a period of time in history or a person's life, typically one marked by notable events or particular characteristics.
- 9. a unit of time equal to a thousand million years.