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List of index fossils
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<p>Index fossils (also known as guide fossils or indicator fossils) are <a href="/facts/Fossil/by7NzIA1">fossils</a> used to define and identify <a href="/facts/Geologic_column/vBAm0D8Q">geologic periods</a> (or faunal stages). Index fossils must have a short vertical range, wide geographic distribution and rapid evolutionary trends. Another term, "zone fossil", is used when the fossil has all the characters stated above except wide geographical distribution; thus, they correlate the surrounding rock to a <a href="/facts/Biozone/ABmwVvme">biozone</a> rather than a specific time period. </p> List of index fossils in chronological order<table><tbody><tr><th>Image</th><th>Scientific Name</th><th>Geological time interval</th><th>Period(million years ago)</th></tr><tr><td><a href="/facts/Argopecten_gibbus/aaRtUeWU">Calico scallop</a></td><td><i><a href="/facts/Atlantic_calico_scallop/aaRtUeWU">Argopecten gibbus</a></i></td><td><a href="/facts/Quaternary/3cEgHAqc">Quaternary</a></td><td>1.8</td></tr><tr><td></td><td><i><a href="/facts/Neptunea/GLM6pPKg">Neptunea tabulata</a></i></td><td><a href="/facts/Quaternary/3cEgHAqc">Quaternary</a></td><td>1.8</td></tr><tr><td></td><td><i><a href="/facts/Viviparus_glacialis/fu7vfzlJ">Viviparus glacialis</a></i></td><td><a href="/facts/Tiglian/Wz8fe7B7">Tiglian</a> (<a href="/facts/Early_Pleistocene/jPp2Cn7a">Early Pleistocene</a>)</td><td>2.3–1.8</td></tr><tr><td></td><td><i>Calyptraphorus velatus</i></td><td><a href="/facts/Tertiary_(period)/Krcz3olj">Tertiary</a></td><td></td></tr><tr><td></td><td><i><a href="/facts/Venericardia/sFrXwf4q">Venericardia planicosta</a></i></td><td><a href="/facts/Eocene/EYgI8Uco">Eocene</a></td><td></td></tr><tr><td><i><a href="/facts/Scaphites/EHyjC8Xl">Scaphites</a></i></td><td><i><a href="/facts/Scaphites_hippocrepis/EHyjC8Xl">Scaphites hippocrepis</a></i></td><td><a href="/facts/Cretaceous/nwKtFtKx">Cretaceous</a></td><td>143.1–66</td></tr><tr><td><i><a href="/facts/Inoceramus/kIccWWjM">Inoceramus</a></i></td><td><i>Inoceramus labiatus</i></td><td><a href="/facts/Cretaceous/nwKtFtKx">Cretaceous</a></td><td></td></tr><tr><td><i><a href="/facts/Perisphinctes/xq2zCnk6">Perisphinctes</a></i></td><td><i>Perisphinctes tiziani</i></td><td><a href="/facts/Jurassic/o5Cy4KzX">Jurassic</a></td><td>201.3–145</td></tr><tr><td></td><td><i><a href="/facts/Nerinea/8qpn9Esd">Nerinea trinodosa</a></i></td><td><a href="/facts/Jurassic/o5Cy4KzX">Jurassic</a></td><td></td></tr><tr><td></td><td><i>Tropites subbullatus</i></td><td><a href="/facts/Triassic/r6CNxKXC">Triassic</a></td><td></td></tr><tr><td></td><td><i>Monotis subcircularis</i></td><td><a href="/facts/Triassic/r6CNxKXC">Triassic</a></td><td></td></tr><tr><td><i>Leptodus</i></td><td><i>Leptodus americanus</i></td><td><a href="/facts/Permian/CYgLgu5u">Permian</a></td><td></td></tr><tr><td><i><a href="/facts/Parafusulina/SoXN06dF">Parafusulina</a></i></td><td><i>Parafusulina bosei</i></td><td><a href="/facts/Permian/CYgLgu5u">Permian</a></td><td></td></tr><tr><td></td><td><i>Dictyoclostus americanus</i></td><td><a href="/facts/Pennsylvanian_(geology)/Fc1LAJSX">Pennsylvanian</a></td><td></td></tr><tr><td></td><td><i>Lophophyllidium proliferum</i></td><td><a href="/facts/Pennsylvanian_(geology)/Fc1LAJSX">Pennsylvanian</a></td><td></td></tr><tr><td></td><td><i>Cactocrinus multibrachiatus</i></td><td><a href="/facts/Mississippian_(geology)/tqsS6Ifj">Mississippian</a></td><td></td></tr><tr><td></td><td><i>Prolecanites gurleyi</i></td><td><a href="/facts/Mississippian_(geology)/tqsS6Ifj">Mississippian</a></td><td></td></tr><tr><td><i><a href="/facts/Mucrospirifer/VPtLkWvT">Mucrospirifer</a></i></td><td><i><a href="/facts/Mucrospirifer_mucronatus/VPtLkWvT">Mucrospirifer mucronatus</a></i></td><td><a href="/facts/Devonian/nWgakqzk">Devonian</a></td><td>416–359</td></tr><tr><td></td><td><i><a href="/facts/Palmatolepis_unicornis/bBF7JPdB">Palmatolepis unicornis</a></i></td><td><a href="/facts/Devonian/nWgakqzk">Devonian</a></td><td></td></tr><tr><td></td><td><i><a href="/facts/Tetragraptus/5ddhMGEy">Tetragraptus fructicosus</a></i></td><td><a href="/facts/Ordovician/BjMrLIEA">Ordovician</a></td><td></td></tr><tr><td></td><td><i><a href="/facts/Paradoxides/mUJdDnby">Paradoxides</a></i></td><td><a href="/facts/Cambrian/jIfzKtod">Cambrian</a></td><td>509–500</td></tr><tr><td></td><td><i>Billingsella corrugata</i></td><td><a href="/facts/Cambrian/jIfzKtod">Cambrian</a></td><td></td></tr><tr><td></td><td><a href="/facts/Archaeocyatha/GPuEv5wA">Archaocyathids</a></td><td><a href="/facts/Cambrian/jIfzKtod">Cambrian</a></td><td>529–509</td></tr></tbody></table>