The earliest known snails were similar in structure to limpets. These creatures lived in shallow sea water and fed on algae and they had a pair of gills. The most primitive of the air-breathing snails (also called pulmonates) belonged to the Family Ellobiidae. Members of this family still lived in water (salt marshes and coastal waters) but they went to the surface for air. Today's land snails evolved not from this group but from the Family Endodontidae, a group of snails that had similar characteristics to the Family Ellobiidae.
Tendencies in Snail Evolution
When we look back through the fossil record, we can see various tendencies in how snails changed over time. In general the following patterns emerge:
- the process of torsion becomes more prominant
- the shell became increasingly conical and spirally coiled
- there is an evolutionary tendency among pulmonates towards the entire loss of a shell