The length of time is not as critical as the traits of being widespread, rapidly evolving, and observable only during a specific period of time.
The relative age of a fossil that can be determined by comparing it to an index fossil is called biostratigraphic dating. This method relies on the known age range of the index fossil to estimate the relative age of the fossil being studied.
it must have lived through a long span of time
Lichens are believed to have existed for hundreds of millions of years. Fossil evidence suggests that lichens have been around since the late Silurian period, dating back over 400 million years.
Yes, ammonites are good index fossils because they had a wide geographical distribution and existed for a long period of time. Their evolution is well-documented, making them useful for relative dating of rock layers.
No, Index fossils are used to date certain rock layers where the fossil is found. So it's usefull when you can find a certain index fossil only in a small period of time. So you can get the most precise dating for the rock layer. Horseshoe crabs are known as a 'living fossil', the first fossils of horse shoe crabs are found 450 millions years ago. So when you find a fossil of a horse shoe crab in a rock or sediment, you can't say anything about the age of the rock.
To be useful as an index fossil fuel, spices must have existed for about 1000 years.
they are only been found in a narrow geographic range
An index fossil is used as an indicator of which era/epoch was preserved. The major characteristic necessary to be an index fossil include abundance, widely distributed, but lived for a short period of time.
A fossil is a trace of an organism that lived long ago.
The relative age of a fossil that can be determined by comparing it to an index fossil is called biostratigraphic dating. This method relies on the known age range of the index fossil to estimate the relative age of the fossil being studied.
it must have lived through a long span of time
species that have existed in a community for a long time is said to have attained stability. :)
The Eurypterids in these cross sections not useful as index fossil because they are only found in certain areas are a long lived organism
The fossil record shows that the kingdom Plantae has existed on Earth for 520 million years.
By using relative age. Over a long period of time, sediment will, layer by layer, coat and cover the fossil, making it difficult for paleontologists and scientists to figure out how old the fossil really is.
Some before the dinosaurs,any better answers?
A living fossil generally refers to a living organism, animal or plant, whose species has been around long enough on the planet to be part of the fossil record. Most fossilized species are extinct, but there are a few which are either still in existence, or have descendents which closely resemble them.