List of index fossils
Index fossils are fossils used to define and identify geologic periods. Index fossils must have a short vertical range, wide geographic distribution and rapid evolutionary trends. Another term, Zone fossil is used when the fossil have all the characters stated above except wide geographical distribution, they are limited to a zone and can't be used for correlations of strata.
| Fossil | Scientific Name | Geological time interval | Million Years Ago |
Calico scallop | Argopecten gibbus | Quaternary | |
| Neptunea tabulata | Quaternary | ||
| Viviparus glacialis | Tiglian | ||
| Calyptraphorus velatus | Tertiary | ||
| Venericardia planicosta | Eocene | ||
Scaphites | Scaphites hippocrepis | Cretaceous | |
Inoceramus | Inoceramus labiatus | Cretaceous | |
Perisphinctes | Perisphinctes tiziani | Jurassic | 201.3 to 145 million years ago |
| Nerinea trinodosa | Jurassic | ||
| Tropites subbullatus | Triassic | ||
| Monotis subcircularis | Triassic | ||
Leptodus | Leptodus americanus | Permian | |
| Parafusulina | Parafusulina bosei | Permian | |
| Dictyoclostus americanus | Pennsylvanian | ||
| Lophophyllidium proliferum | Pennsylvanian | ||
| Cactocrinus multibrachiatus | Mississippian | ||
| Prolecanites gurleyi | Mississippian | ||
Mucrospirifer | Mucrospirifer mucronatus | Devonian | |
| Palmatolepis unicornis | Devonian | ||
| Tetragraptus fructicosus | Ordovician | ||
| Paradoxides | Cambrian | ||
| Billingselia corrugata | Cambrian | ||
| Archaocyathids | Cambrian |