List of index fossils

{{short description|Fossils used to define and identity geologic periods}}

Image:Index fossils.gif. Updated July 31, 1997.]]

{{Paleontology}}

Index fossils (also known as guide fossils or indicator fossils) are fossils used to define and identify 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 (million years ago)
120px Calico scallop	Argopecten gibbus	Quaternary	1.8
	Neptunea tabulata	Quaternary	1.8
120px	Viviparus glacialis	Tiglian (Early Pleistocene)	2.3–1.8
	Calyptraphorus velatus	Tertiary
	Venericardia planicosta	Eocene
120px Scaphites	Scaphites hippocrepis	Cretaceous	143.1–66
120px Inoceramus	Inoceramus labiatus	Cretaceous
120px Perisphinctes	Perisphinctes tiziani	Jurassic	201.3–145
	Nerinea trinodosa	Jurassic
	Tropites subbullatus	Triassic
120px	Monotis subcircularis	Triassic
120px Leptodus	Leptodus americanus	Permian
Parafusulina	Parafusulina bosei	Permian
	Dictyoclostus americanus	Pennsylvanian
	Lophophyllidium proliferum	Pennsylvanian
	Cactocrinus multibrachiatus	Mississippian
	Prolecanites gurleyi	Mississippian
120px Mucrospirifer	Mucrospirifer mucronatus	Devonian	416–359
	Palmatolepis unicornis	Devonian
	Tetragraptus fructicosus	Ordovician
120px	Paradoxides	Cambrian	509–500
	Billingsella corrugata	Cambrian
120px	Archaocyathids	Cambrian	529–509