Reptiles and birds are divided into two classes, reptilia and aves. what fossil evidence would be the best support for this division? a) amniotic eggs of birds b) presence of reptilian scales c) air chambers in the bird skeletons d) warm-bloodedness of birds versus cold-bloodedness of reptiles

The correct answer is the air chambers in the bird skeletons. First of all, both reptiles and birds have amniotic fluids; and this cannot be documented by fossil studies. While it is true that birds do not have reptilian scales, this cannot be documented by fossil studies too. Warm bloodedness of birds and cold bloodedness of reptiles cannot also be documented by fossil studies. Air chambers in the bird skeleton, on the other hand, can be seen as fossil evidence and differentiated with reptilian skeletons with no air chambers. 

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