Life then and now

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Across
  1. 6. the way in which an animal or person acts in response to a particular situation
  2. 7. an action or process of discovering or being discovered
  3. 8. internal or external framework of bone or cartilage
  4. 12. an animal that eats plants and animals
  5. 13. something has vanished, lost or destroyed
  6. 14. animals lacking a backbone
  7. 15. an animal that naturally prey's an others
Down
  1. 1. large group of animals with a backbone or spinal column
  2. 2. framework of the mouth and containing teeth
  3. 3. a fossil reptile of the Mesozoic era
  4. 4. an animal that is being hunted by another animal
  5. 5. animals that only eat meat
  6. 9. any remains or impressions like skeleton or footprint
  7. 10. belonging to the very distant past and no longer in existence
  8. 11. animal that eats only plants