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Across 4. A fluid filled neuroglial cavity housed within the spinal cord. 5. These organs are present only in females and provide milk to feed offspring. 6. This subclass has two pairs of temporal openings and consists of many modern day animals such as crocodiles, snakes and lizards. 7. The age in which reptiles were originally formed. 10. Part of the mammalian brain, in humans it is the largest part of the cerebral cortex. 12. An organism that has a diet consisting of meat. 15. This man was responsible for creating the classification system and many other things in the field of biology. 16. These determine whether the resulting offspring is male or female. 17. Kingdom, _______, Class, Family, Species. 20. This infraclass of mammals has a distinct feature, a pouch in which they carry their young. 21. This Order of amphibians consists of multiple snake and earthworm type animals. 24. A Class that consists of many families including humans. 25. A distinct trait among birds and essential for flight. 26. An armor or skin texture that protects animals and insulates them.

Down 1. This subclass of the class Reptilia is distinct in it’s characteristic of having temporal openings in the skull, and has turtles as its only present day species. 2. This man published a book that was considered to be "...the beginning of scientific ornithology in Europe, revolutionizing ornithological taxonomy by organizing species according to their physical characteristics." 3. A ______ is a distinct juvenile form many animals undergo before metamorphosis into adult. 6. This characteristic of amphibians means " 8. Chromosomes pairing at meiosis and having the same structural features and pattern of genes. 9. This Class contains any amniote that isn't a bird or mammal. 11. This characteristic is seen in any non-mammal creature, typically reptiles and birds. 13. This trait is seen most commonly in reptiles and fish, requiring them to warm themselves by basking in sunlight. 14. This term describes a process in which the system absorbs energy in the form of heat from its surroundings. 18. This organ connects the fetus to the uterine wall to allow waste elimination, nutrient uptake, and gas exchange. 19. This family is largely comprised of aquatic birds with heavy bodies, short legs, webbed feet, and distinct beaks or bills. 22. This Order of the class Amphibia includes frogs and toads. 23. This class has approximately ten thousand different species.