The largest egg in the world could be sold for as much as £50,000 when it is auctioned at Billingshurst in November.
The egg, belonging to the extinct elephant bird, is more than a foot in length, and engineers believe it is ‘impossible for an egg to be any larger’.
It is expected to fetch between £30,000 and £50,000 when it is sold by Summers Place Auctions in Billingshurst on Wednesday November 26.
Errol Fuller, curator of the sale, said: “ I have written several books on extinct birds and the elephant bird has always been particularly fascinating.
“The egg of one of these birds is simply a miracle, it’s over a foot in length (30cm) and larger than any known dinosaur egg.
“In fact it is the largest egg ever recorded and engineers have calculated that structurally and functionally it is impossible for an egg to be any larger.”
Elephant birds grew to more than 3m in height and weighed around half a tonne. It is believed the species became extinct around the 17th century.
The rare egg is large enough to hold the contents of seven ostrich eggs, 100 chicken eggs or 12,000 hummingbird eggs.
The item is part of the auction house’s second Evolution sale - last year, the auction house sold a 55ft long complete Diplodocus Longus skeleton, which had been nicknamed Misty.
It was bought by the Natural History Museum of Denmark for £483,100, and the dinosaur was set to go on display in Copenhagen.
More than 50 lots from a private German collection of fossils will also be included in the sale.
These include a fossil of the large marine reptile Ichthyosaur, which is almost 150cm long and carries an estimate of £8,000 to £12,000.
An ichthyosaur head and foreparts, and an ichthyosaur head, both valued at £7,000 to £9,000, are also included – all are from the early Jurassic period.
Skeletons including that of a moa, an extinct flightless bird from New Zealand, will be sold in the region of £70,000 to £90,000.
An extinct cave bear’s skeleton will cost between £15,000 and £20,000, while an ostrich skeleton could fetch £5,000 to £8,000.
The auction will also please customers hoping to buy their own unicorn - taxidermy made from a horse and a narwhal tusk is expected to sell for £5,000 to £8,000.
Other unusual taxidermy lots, including the extinct passenger pigeon and part of a tiger, will also be available during the sale.