Snails are ancient survivors. While dinosaurs appeared around 230 million years ago and went extinct 66 million years ago, snails have been crawling across Earth for over 500 million years. They have survived every mass extinction event in Earth's history — including the one that wiped out the dinosaurs.
Timeline of Snail Evolution
| Period | Years Ago | Event |
|---|---|---|
| Cambrian | ~530 million | First gastropod-like mollusks appear in the sea |
| Ordovician | ~480 million | Diverse marine gastropods established |
| Devonian | ~350 million | Land colonisation begins — first terrestrial snails |
| Carboniferous | ~300 million | Land snails diversify in swamp forests |
| Cretaceous | ~100 million | Modern snail families recognisable |
| Eocene | ~50 million | Spread to all continents including Antarctica |
| Today | — | 60,000+ species of snail and slug worldwide |
How Did Snails Move onto Land?
The move from sea to land is one of evolution's most remarkable transitions. Snails achieved it gradually — early ancestors lived in coastal intertidal zones, then freshwater, then damp soil, and eventually dry land. Key adaptations included developing a tougher mantle to reduce water loss, a more efficient kidney for water retention, and — crucially — a radula well-suited to the fibrous plant material found on land.
The Radula: A 500-Million-Year-Old Innovation
The radula evolved in the earliest mollusks and has remained the defining feature of the group ever since. It is one of the oldest continuously used feeding structures in animal evolution. The basic design — a flexible, muscular ribbon covered in teeth — has been refined and adapted across 500 million years into the extraordinary variety seen today, from the garden snail's rasping structure to the limpet's iron-tipped teeth.
How Many Snail Species Exist Today?
Gastropods (the group containing snails and slugs) are the most diverse class of mollusks, with an estimated 65,000–80,000 described living species. Many more remain undescribed, particularly in tropical regions. Snails are found on every continent, in every ocean, and at altitudes above 5,000 metres.