Big bird: Experts unveil skull of giant duck with teeth and the wingspan of a family car

They are ducks - but not as we know them.

Instead of the fluffy little creatures seen today, these big birds boasted 'teeth', a 16ft wingspan and once flew over Britain.

Today, scientists announced the discovery of fossil skulls of these birds buried in clay on the Isle of Sheppey in Kent.

It is not the first time fossils of these duck have been found, but the experts believe this find is among the best-preserved.

The enormous birds, known as Dasornis, soared over the wetlands of prehistoric southern England when the land which now covers London, Essex and Kent was underwater.

Related to present-day ducks and geese, 50 million years ago these giants once skimmed the waters, snapping up fish and squid with their bony-toothed beak.

Their massive wingspan - the length of a family car - also meant they could cover huge distances. Dasornis was in many ways similar to the modern albatross.

Dr Gerald Mayr, from the Senckenberg Research Institute in Frankfurt, Germany, who described the find today in the journal Palaeontology, said: 'Imagine a bird like an ocean-going goose, almost the size of a small plane.

'By today's standards these were pretty bizarre animals, but perhaps the strangest thing about them is that they had sharp, tooth-like projections along the cutting edges of the beak.

'Like all living birds, Dasornis had a beak made of keratin, the same substance as our hair and fingernails, but it also had these bony "pseudo-teeth".

'No living birds have true teeth because their distant ancestors did away with them more than 100 million years ago, probably to save weight and make flying easier.

'But the bony-toothed birds, like Dasornis, are unique among birds in that they reinvented tooth-like structures by evolving these bony spikes.'

The fossil is in a collection at the Karlsruhe Natural History Museum, Germany.