Across
- 4. warm-blooded vertebrate with fur/hair
- 6. Earliest eon of the earth
- 7. Vertebrates with scales and tough skin
- 8. When an organism mutates to survive
- 11. Formed from other rocks changed by heat
- 15. Animals with backbones
- 16. Formed from pre-existing rocks
- 17. Hollow fossil imprinted in substrate
- 18. Present day
- 20. Animals matter is replaced by minerals
- 21. Remain of an animals in a rock
- 22. A person who studies the earth
- 23. Decayed remains in a rock
Down
- 1. Smallest thing in the world
- 2. A person who studies fossils
- 3. The tracks of a prehistoric animal
- 5. Age of the dinosaurs
- 9. Rock made from hardened lava
- 10. Age of the reptiles
- 12. A long and distinct period of history
- 13. Animals without backbones
- 14. Geological events
- 19. When a species is wiped off the earth