1. A small, organic-walled microfossil of unknown biological origin, typically found in marine sediments from the Proterozoic and Paleozoic eras.
Usage: paleontology; geology; technical

Examples

• Acritarchs are commonly used by paleontologists to date and correlate ancient rock layers.
• The discovery of acritarchs in the sediment core provided evidence of early marine life.
• Acritarch assemblages help geologists understand the environmental conditions of the Precambrian ocean.
• These microscopic acritarchs are preserved in shale and limestone deposits worldwide.
• Scientists study acritarch morphology to infer the evolutionary history of early eukaryotes.