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Across 4. A birds entire anatomy is designed around ____. 5. What do modern reptiles represent? 9. A type of cell that give lizards and snakes their colorful hues. 12. Lizards have ___ ___ (except in most gekos) whereas snakes have a transparent covering. 13. ____ of birds often reveal their food habits. 15. These reptiles have a greatly elongated snout. 16. Nonvenomous snakes kill by biting and swallowing. What is the other way they kill? 17. These appeared in the fossil record in the Jurassic period but did not diversify until the Cretaceous. 22. Amniotes arose from amphibian-like tetrapods, the ____, suring the Carboniferous. 25. Worm lizards have eyes and ___ hidden under their skin. 26. Most snakes are ___ and lay shelled eggs. 28. Many birds have a ____ that serves to store food at lower end of esophagus. 29. Total weight of a bird's feathers may ____ skeleton. 31. Developing young enclosed by extraembryonic membrane called the _____. 34. Nearly all birds lay eggs that must be ____ by one or both parents. 35. Nearly one-fifth of birds feed on _____. 36. Reptiles can store ___ in tails to provide energy and metabolic water during drought. 37. ____ reptiles have tough, dry, scaly skin that protects against desiccation and physical injury. 38. In birds what is the end of the digestive system called? 39. Viper fangs are hollow and hinged to inject what?

Down 1. What subclass has a skull with two temporal openings? 2. Pair of pits in the roof of the mouth are part of what? 3. Snakes have a ___ ____ skull that allows them to eat prey several times their own diameter. 6. Mothers in the order Crocodilia respond to ___ from hatchlings young. 7. Males of most species of birds lack a _____. 8. What is it when a snake has a primitive placenta to exchange nutrients with the young? 10. A land-dweller they do not have webbed feet. 11. What is the unique and essential feature or hallmark of birds? 14. Bird feather is ___ to reptile scale. 15. Foods that require grinding are cut apart in the _____. 18. Lizards keep body temperature relatively constant aalthough they are what? 19. The tuatara have a well-developed median ____ ____ buried beneath their skin. 20. What subclass includes the order Testudines? 21. Most reptiles have ___ vision. 23. What is thick and tends to be more keratinized and less permeable to water? 24. What order only has two living species in New Zealand? 27. What is the most common form of polygamy? 30. Platelike modified scales. 32. Fertilization in birds takes place in the upper _____. 33. In reptiles and birds, what aids in gas exchange?