Across
- 2. you are this mammal
- 5. an approximate time
- 6. began 541 million years ago with the Cambrian explosion
- 9. the amount of time it takes for half of a remaining isotope to decay to a daughter product.
Down
- 1. human era
- 3. dinosaur era
- 4. giant animal that dominated the land for millions of years
- 7. the exact age
- 8. 1 billion years
- 10. animal remains