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The 14 pages that link to Index fossil, each with the reason it gives.

• FossilBroader topic: Its limited time range makes it useful for dating strata relatively.

• Fossil recordBroader topic: Its restricted time range helps assign ages to fossil-bearing rocks.

• BiostratigraphyRelated: Its limited time range and broad distribution make correlation more precise.

• AmmoniteNarrower topic: Rapid evolution and broad distribution made many ammonite species effective index fossils.

• Deep timeBroader topic: These fossils let geologists match distant strata without relying on identical rock types.

• William SmithRelated: Smith recognized that characteristic fossils could help match distant rock exposures.

• TrilobiteRelated: Some trilobite species had limited time ranges and broad geographic distributions.

• Relative datingBroader topic: Its limited time range can sharply constrain a layer's relative position.

• Stratigraphic correlationRelated: Its limited time range makes its occurrence a more precise tie between rock units.

• Geologic timeRelated: Its limited time range helps match strata and locate interval boundaries.

• North American land mammal ageRelated: Some characteristic mammals help identify particular intervals across separate localities.

• AmmonoideaRelated: Ammonoid fossils evolved rapidly and spread widely, making them useful for dating rocks.

• MicropaleontologyRelated: Short-ranging microfossil species can mark precise intervals in sedimentary rocks.

• Geologic recordBroader topic: Its limited time range helps match distant parts of the record.