The fossilised remains of the largest flying bird ever found have been identified by scientists.
Pelagornis sandersi would have looked similar to a seagull... if seagulls weighed 180lb and had 24ft wingspans.
Twice the size of an albatross – the largest living bird – it would have required a running jump into a headwind to take off.
Computer simulations suggest that once in the air, it would have been highly skilled in flight - but its stumpy legs and hollow bones would mean landing was tricky.
The 25 million-year-old fossil was discovered 30 years ago in South Carolina, US, but it has taken until now to confirm it is a new species.
Construction workers discovered the bones while digging a new terminal at the Charleston International Airport.
Dr Dan Ksepka, curator of science at Bruce Museum in Connecticut, said: "It would have been fast and very efficient.
"Computer models suggest that it had high lift-to-drag ratios, which would allow it to glide for a very long distance.
"It could likely glide at speeds over 10m per second - faster than the human world record for the 100m dash."
Its size and beak suggested it was a previously unknown species of pelagornithid - an extinct group of giant seabirds believed to be ancestors of pelicans and storks.
They were known for bony 'teeth’ that lined their jaws, a study published in the Proceedings of the National Academy of Sciences reported.
Huge birds like this vanished about three million years ago but scientists do not yet understand why.