a paleospecies that had a very wide geographical distribution but existed for a relatively short period of time, either becoming extinct or evolving into something else.
A fossil that is specific to one geographic era or geological time.
A fossil that identifies and dates the strata in which it was found. Common index fossils include graptolites and ammonites.
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
a fossil from an organism, about which we have a clear understanding when it lived, or the conditions under which it lived
a fossil that is useful in working out the age of a bed of rock
a particular type of fossil presumed to identify rock formations or strata
a useful tool for telling the age of the rock it was deposited in
a geographically widespread fossil, that is diagnostic of a particular time period and therefore useful in correlating the age of rock formations from different geographic areas
A fossil that helps to determine the identity or age of a particular rock unit. Invertebrate: An animal that does not have a backbone. Ex: arthropods, mollusks, brachiopods, echinoderms.
The fossil of an organism known to have existed for a relatively short period of time, used to date the rock in which it is found.
Index fossils are commonly found fossils that are limited in time span. They help in dating other fossils. For example: trilobites were common during the Paleozoic, but not found before the Cambrian period. Ammonites were common during the Mesozoic Era, but not found after the Cretaceous period. Another example: the oldest-known ostracods (tiny freshwater and marine crustaceans (see)) are from the Cambrian period; they became widespread during the Ordovician and remain so.
a fossil that is used to date the rock layers in which it is found; the original organism must have lived during a relatively short, well-defined time span and have a wide geographic distribution
A fossil which evolutionary geologists claim to be from a certain time period because its found in certain strata. They use circular reasoning, dating the rocks from the fossils and the fossils by the rocks.
A fossil that identifies and dates the strata in which it is found, especially it commonly found or found over a large part of the earth, and lived for only a short time range.
the fossil remains of an organism that lived in a particular geologic age, used to identify or date the rock or strata in which it is found. [AHDOS
Index fossils (also known as guide fossils or zone fossils) are fossils used to define and identify geologic periods (or faunal stages). They work on the premise that, although different sediments may look different depending on the conditions under which they were laid down, they may include the remains of the same species of fossil. If the species concerned were short-lived (in geological terms, lasting a few hundred thousand years), then it is certain that the sediments in question were deposited within that narrow time period.