Marine diversification filled seas with trilobites, brachiopods, bryozoans, crinoids, nautiloids, graptolites, and early vertebrates.
Approximate span485–444 million years ago
Best evidenceAnatomy + stratigraphy
Collector ruleKeep formation data
Common collector material
- trilobites
- brachiopods
- nautiloids
- graptolites
Using the period in identification
The period provides a plausibility test. Compare the claimed organism’s known temporal range with the formation, locality, matrix, and associated fossils. A correct period cannot rescue incorrect anatomy, and a familiar-looking fossil can still be mislabeled when it comes from the wrong unit.
Marketplace cautions
- Rounded ages may differ by tens of millions of years.
- “Dinosaur age” is often applied broadly to any Mesozoic material.
- Reworked fossils can erode from older rocks and become deposited in younger sediments.
- Commercial formation names may be incomplete, outdated, or used as regional shorthand.
Collection record
Record both the seller’s stated age and the evidence supporting it. Preserve the original label even if later research changes the interpretation.
Build a comparison set
Repeatable method: use the identification workflow, authenticity guide, legal and ethical guide, and value guide. This page focuses on specimen-specific morphology, locality, preparation, or collecting context.
Compare collector listings Check sold & completed listings