Across
- 3. age of fishes 416 million years ago
- 4. era of the dinosaurs
- 7. an animal without a backbone
- 8. an animal with a backbone
- 11. first amphibians and reptiles 359 million years ago
- 14. celled first living organisms
- 15. age of reptiles 251 million years ago
- 16. event that caused mass extinction of the dinosaurs
- 17. an animal that lives in water and on land
Down
- 1. first vertebrates evolve
- 2. a single land mass
- 5. no longer living
- 6. 4.6 Billion years ago
- 9. Age of the Dinosaurs 200 million years ago
- 10. pangaea forms
- 12. first insects 444 million years ago
- 13. an explosion of life forms 542 million years ago