Across
- 2. Continents form to modern day
- 3. layered sedimentary formations
- 4. Reptiles ruled the world
- 8. time Longest Earth era
- 10. Age of dinosours
- 11. organisms with a back bone
- 12. process of change over time in organisms
- 13. colonial extinct animals
- 15. freshwater fish
- 17. Close to modern day mammles lived
- 18. part of hard sedimentary rock
- 19. lots of swampy dense forest
- 21. long era of the earth with 7 periods
Down
- 1. last period of the paleozoic era
- 5. fish closely related to lung fish
- 6. group of extinct animals with hard valves
- 7. organisms with no backbone
- 9. period of time when fish ruled the sea
- 14. group of extinct marine arthopods
- 16. Decrease of a population in a short amount of time
- 20. extinct organisms often called sea scorpians
- 21. Super continent of modern day continents