What does "index fossil" mean?

Any ancient remains of a plant or animal that lived during a specific geological period and that can be used to date the containing rocks.

Index fossil

Common synonyms include: belemnite, centric fossil, geology education term, guide fossil, nummulite, seashells.

noun

noun ·Rare ·Advanced level

Noun

1
Any ancient remains of a plant or animal that lived during a specific geological period and that can be used to date the containing rocks.
2
a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found wordnet