Fossil Gastropods
Snails, limpets, and whelks — gastropods are the largest class of molluscs and have occupied every habitat on Earth for over 500 million years.
Overview
Gastropods — snails and their relatives — are the largest and most varied class of molluscs, occupying every marine habitat plus freshwater and land. Their single coiled shell fossilises readily, giving them a continuous 500-million-year record.
Quick Facts
Key Characteristics
- •Single, usually coiled shell (univalve)
- •Torsion — rotation of the body during development — defines the class
- •Radula ribbon of teeth for scraping or predation
- •Operculum 'trapdoor' closing the shell in many forms
- •Shell sculpture (ribs, spines, varices) records growth and defence
Fossil Record
Gastropod shells occur in nearly every marine deposit — Devonian to Pleistocene. Naticid and muricid drill holes in prey shells are a classic fossil record of predation; exceptional deposits preserve colour patterns.
Global Distribution
Global — the most ubiquitous shelly fossils after bivalves, on every continent.
Evolutionary & Scientific Importance
Gastropods chart the evolution of predator-prey arms races (drilling predation), repeated invasions of fresh water and land, and modern-community assembly in the Cenozoic.
Classification
Older 'Archaeogastropoda' groupings are paraphyletic and superseded by the modern subclasses listed above.