Which fossil is a good index fossil?

marine organisms
A good index fossil is one with four characteristics: it is distinctive, widespread, abundant, and limited in geologic time. Because most fossil-bearing rocks formed in the ocean, the major index fossils are marine organisms. That being said, certain land organisms are useful in young rocks and specific regions.

What is the best index fossil and why?

The best index fossils are common, easy-to-identify at species level, and have a broad distribution—otherwise the likelihood of finding and recognising one in the two sediments is low. Ammonites fit these demands well, and are the best-known fossils that have been widely used for this.

Why are trilobites important as index fossils check all answers that apply?

Trilobites make good index fossils because they evolved quickly and rapidly spread in abundance across the world during the middle of the Cambrian…

Which two reasons contribute to the good fossil record of trilobites?

The abundance of trilobite fossils is partly due to the fact that they, like all arthropods, molted throughout growth, and that the biomineralized exoskeleton was already present in early larval stages.

Which organism makes the best index fossil?

Different species of trilobite fossils can be used to narrow the age even more. Trilobites are good index fossils.

Which organism is not used as index fossil?

3. Name three organisms represented that probably could not be used as index fossils and explain why. The brachiopod, crinoid, eurypterid, foraminifera, gastropod, horn coral, pelecypod, and trilobite could probably not be used as index fossils since they overlap more than one stratum.

Why are index fossils so important?

Index fossils help scientists to determine the approximate age of a rock layer and to match that layer up with other rock layers. Fossils give clues about the history of life on Earth, environments, climate, geologic history, and other events of geological importance.

Why does a shellfish like a trilobite fossil make a good index fossil?

These cephalopods make for ideal index fossils because they are abundant, widespread, and their various species lived during distinct time periods that can be easily identified by their suture patterns.

What is special about trilobites?

Trilobita is the most species-rich entirely extinct arthropod group. In trilobites, the hard exoskeleton covering the dorsal body surface and its well marked segmentation (for example, the jointed segments of the thorax) are classic arthropod features. The trilobite exoskeleton was mineralised, constructed of calcite.

Why are trilobite fossils black?

Importantly, Moroccan trilobites from the Ordovician and Cambrian exhibit different exoskeleton colors from those of the Devonian. Because mineral replacement, the preserved exoskeleton normally contains hydrated iron oxides, resulting in colors that are shades of ochre, brown or orange, rather than yellow or black.

Which organism can be considered an index fossil?

Ammonites
Ammonites, trilobites, and graptolites are often used as index fossils, as are various microfossils, or fossils of microscopic organisms. Fossils of animals that drifted in the upper layers of the ocean are particularly useful as index fossils, as they may be distributed all over the world.