Browse Fossils by Geologic Age
Connect fossil groups to the periods, environments, and formations in which they occur.
Time narrows the possibilities.
A claimed taxon must fit both the anatomy and the age of the rock. Use these pages as orientation, then consult formation-specific and taxonomic references.
Precambrian Fossils
Before 539 million years ago — Microbial mats, stromatolites, microfossils, and late Precambrian soft-bodied organisms dominate a record that requires exceptional contextual evidence.
Open guide →Ediacaran Period Fossils
635–539 million years ago — Soft-bodied organisms, microbial structures, and trace fossils mark a major transition before the Cambrian diversification.
Open guide →Cambrian Fossils
539–485 million years ago — Early animal diversification produced trilobites, brachiopods, archaeocyaths, sponges, and unusual soft-bodied assemblages.
Open guide →Ordovician Fossils
485–444 million years ago — Marine diversification filled seas with trilobites, brachiopods, bryozoans, crinoids, nautiloids, graptolites, and early vertebrates.
Open guide →Silurian Fossils
444–419 million years ago — Reefs expanded, jawed fishes diversified, and terrestrial ecosystems began leaving clearer evidence.
Open guide →Devonian Fossils
419–359 million years ago — Often called the Age of Fishes, with placoderms, sharks, ammonoids, corals, trilobites, and early forests.
Open guide →Carboniferous Fossils
359–299 million years ago — Coal forests, giant arthropods, crinoid-rich seas, amphibians, and early reptiles characterize many collections.
Open guide →Permian Fossils
299–252 million years ago — Synapsids, reptiles, diverse marine invertebrates, and seed plants precede the largest known mass extinction.
Open guide →Triassic Fossils
252–201 million years ago — Early dinosaurs, marine reptiles, ammonoids, conifers, and recovering marine communities followed the end-Permian extinction.
Open guide →Jurassic Fossils
201–145 million years ago — Ammonites, marine reptiles, dinosaurs, fish, plants, and fine-grained conservation deposits define classic collecting material.
Open guide →Cretaceous Fossils
145–66 million years ago — Flowering plants spread while dinosaurs, marine reptiles, ammonites, sharks, fish, and diverse invertebrates flourished.
Open guide →Paleogene Fossils
66–23 million years ago — Mammals, birds, sharks, fish, insects, and flowering plants diversified after the end-Cretaceous extinction.
Open guide →Neogene Fossils
23–2.58 million years ago — Modern-looking mammal and marine communities include horses, proboscideans, whales, sharks, and abundant mollusks.
Open guide →Pleistocene Fossils
2.58 million–11,700 years ago — Ice Age mammals, birds, shells, and plants overlap with human history and frequently require careful age and legal assessment.
Open guide →Quaternary Fossils
2.58 million years ago–present — The youngest geologic period includes Pleistocene fossils and Holocene subfossil material, where “fossil” versus recent can be difficult to establish.
Open guide →