index fossil

ریشه

From the Latin 'index' (pointer, informer, list) + 'fossil' (the remains or impression of a prehistoric organism).

مثال

• The trilobite is an index fossil commonly found in rocks from the Paleozoic era.
• The presence of the ammonite indicates the age of the rock layer, making it an index fossil.
• Index fossils are important for determining the relative age of different geological formations.