These fossils are very useful for us because we can use them to date the layers of rock that they are found in. Fossils that can be used in this way are called index fossils, and rock layers with the same index fossils in them can be correlated. Not my answer, link here for full
http://peter-mulroy.squarespace.com/correlating-rock-layers/
That way they can get the average result and they're usually more accurate.
Regulation of a system by the output.
B) 70 million years
Because it is a little below 60 million years meaning it is a little older than 60 million years
