List of index fossils
Fossils used to define and identity geologic periods
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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.
Fossil | Scientific Name | Geological time interval | Million Years Ago |
---|---|---|---|
Calico scallop | Argopecten gibbus | Quaternary | 1.8 million years ago |
Neptunea tabulata | Quaternary | 1.8 million years ago | |
Viviparus glacialis | Tiglian (Early Pleistocene) | 0.5 million years ago | |
Calyptraphorus velatus | Tertiary | ||
Venericardia planicosta | Eocene | ||
Scaphites | Scaphites hippocrepis | Cretaceous | 145 to 66 million years ago |
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 | 416 to 359 million years ago |
Palmatolepis unicornis | Devonian | ||
Tetragraptus fructicosus | Ordovician | ||
Paradoxides | Cambrian | 509 to 500 million years ago | |
Billingsella corrugata | Cambrian | ||
Archaocyathids | Cambrian | 529 to 509 million years ago |
See also
References
- ^ Index Fossils, from the US Geological Survey. Updated July 31, 1997.