1. Microscopic organic-walled fossils of uncertain biological origin, typically found in marine sediments from the Proterozoic and Paleozoic eras.
Usage: paleontology; plural form; singular is acritarch; technical/scientific term

Examples

• Paleontologists studied acritarchs extracted from rock samples to date the ancient sediment layers.
• The abundance of acritarchs in the core sample suggested a marine depositional environment.
• Acritarchs are useful biostratigraphic markers for correlating rock formations across different regions.
• These microscopic fossils, known as acritarchs, may represent the remains of early algae or other microorganisms.
• The diversity of acritarch morphologies has helped scientists understand the evolution of early life in the oceans.