An international team of scientists led by Dr Kate Sanders from the University of Adelaide, and including Dr Mike Lee from the South Australian Museum, has uncovered how some sea snakes have developed 'shrunken heads' - or smaller physical features than their related species.

Their research is published today in the journal Molecular Ecology.

A large head - "all the better to eat you with" - would seem to be indispensable to sea snakes, which typically have to swallow large spiny fish. However, there are some circumstances where it wouldn't be very useful: sea snakes that feed by probing their front ends into narrow, sand eel burrows have evolved comically small heads.

The team has shown normal-shaped sea snakes can evolve such "shrunken heads" very rapidly. This process can lead to speciation (one species splitting into two).