Fossil species that are used to distinguish one layer from another are called index fossils. Index fossils occur for a limited interval of time. Usually index fossils are fossil organisms that are ...

Ammonite shells are used today as index fossils, meaning they can help date other fossils that are found in the same layer of marine rock. These cephalopods make for ideal index fossils because ...

Because some ammonites only lived during specific periods, when geologists find such fossils, they know the age of the geological structure — this makes ammonites index fossils. Ammonites are ...

It paved the way for a better understanding of geological time. Index fossils are used to work out the age of sedimentary rocks. They’re chosen on the basis of being very common fossils that are found ...

We are collecting and imaging lots of modern and fossil Ginkgo leaves, including leaves submitted by citizen scientists across the nation, in order to help us better understand how variable the ...

Fossil species that are used to distinguish one layer from another are called index fossils. Index fossils occur for a limited interval of time. Usually index fossils are fossil organisms that are ...