By looking at animal fossils, Reed can make deductions about the vegetation and climate of the surrounding region. All are interdependent. And based on what they eat, their chewing design is different. By making specific measurements, Reed can determine whether an animal ate grass, leaves, both, or whether it ate meat, meat and bones, or insects. An animal's bones hold even more clues.
Bone structure can reveal how certain creatures moved.
This in turn can provide information about the landscape. For example, tree climbing primates have different elbow structure than their earthbound cousins. When Reed finds the bones of tree-dwellers, she knows that the area once supported forests. She also knows that the area needed plenty of rain to support all those trees. The thing I'd really like to know is the seasonality.