Editing List of index fossils (section)

{{short description|Fossils used to define and identity geologic periods}}
[[Image:Index fossils.gif|thumb|upright=1.4|Examples of index fossils<ref name="USGS_indexfossils">[http://pubs.usgs.gov/gip/geotime/fossils.html Index Fossils], from the [[US Geological Survey]].  Updated July 31, 1997.</ref>]]
{{Paleontology}}
'''Index fossils''' (also known as guide fossils or indicator fossils) are [[fossil]]s used to define and identify [[geologic column|geologic periods]] (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 [[biozone]] rather than a specific time period. 
{| class="wikitable" align="center"
|+List of index fossils in chronological order
! Image !! Scientific Name !! Geological time interval !! Period<br>(million years ago)
|-
|[[Image:Calico scallop 02.jpg|120px]]<br />[[Argopecten gibbus|Calico scallop]]||<br />''[[Atlantic calico scallop|Argopecten gibbus]]'' || [[Quaternary]] || 1.8
|-
| || ''[[Neptunea|Neptunea tabulata]]'' || [[Quaternary]] || 1.8
|-
|[[Image:Viviparus glacialis - Rosmalen - Late Tiglian.jpg|120px]]|| ''[[Viviparus glacialis]]'' || [[Tiglian]] ([[Early Pleistocene]]) || 2.3–1.8
|-
| || ''[[Calyptraphorus velatus]]'' || [[Tertiary]] ||
|-
| || ''[[Venericardia|Venericardia planicosta]]''  || [[Eocene]] ||
|-
|[[Image:SmallScaphites.jpg|120px]]<br />''[[Scaphites]]'' || ''[[Scaphites hippocrepis]]'' || [[Cretaceous]] || 143.1–66
|-
|[[Image:InoceramusCretaceousSouthDakota.jpg|120px]]<br />''[[Inoceramus]]'' ||''[[Inoceramus labiatus]]'' || [[Cretaceous]] ||
|-
|[[Image:Ammonit - Wüstenhaus.jpg|120px]]<br />''[[Perisphinctes]]'' || ''[[Perisphinctes tiziani]]'' || [[Jurassic]] ||201.3–145
|-
| || ''[[Nerinea|Nerinea trinodosa]]'' || [[Jurassic]] ||
|-
| || ''[[Tropites subbullatus]]'' || [[Triassic]] ||
|-
|[[File:Monotis fossil shells - Kiritehere beach.jpg|120px]] || ''[[Monotis subcircularis]]'' || [[Triassic]] ||
|-
|[[Image:Leptodus100711.jpg|120px]]<br />''[[Leptodus]]'' || ''[[Leptodus americanus]]''   || [[Permian]] || 
|-
|''[[Parafusulina]]'' || ''[[Parafusulina bosei]]'' || [[Permian]] ||
|-
| || ''[[Dictyoclostus americanus]]''    || [[Pennsylvanian (geology)|Pennsylvanian]] ||
|-
| || ''[[Lophophyllidium proliferum]]'' || [[Pennsylvanian (geology)|Pennsylvanian]] ||
|-
| || ''[[Cactocrinus multibrachiatus]]'' || [[Mississippian (geology)|Mississippian]] || 
|-
| || ''[[Prolecanites gurleyi]]''        || [[Mississippian (geology)|Mississippian]] ||
|-
|[[Image:Mucrospirifer mucronatus Silica Shale.JPG|120px]]<br />''[[Mucrospirifer]]'' || ''[[Mucrospirifer mucronatus]]'' || [[Devonian]] ||416–359
|-
| || ''[[Palmatolepis unicornis]]'' || [[Devonian]] ||
|-
| || ''[[Tetragraptus|Tetragraptus fructicosus]]'' || [[Ordovician]] ||
|-
| [[File:BLW Trilobite (Paradoxides sp.).jpg|120px]]
|| ''[[Paradoxides]]''        || [[Cambrian]] || 509–500
|-
| || ''[[Billingselia corrugata|Billingsella corrugata]]''   || [[Cambrian]] ||
|-
|[[Image:Archeocyathids.JPG|120px]] || [[Archaeocyatha|Archaocyathids]] || [[Cambrian]] || 529–509
|}