A giant semi-fossilised egg that is almost 100 times larger than a chicken 's egg and still has the tiny skeleton of a bird inside is to go on sale for more than £50,000 . The rare egg , which is 12 inches long and more than eight inches in diametre , belonged to the now extinct elephant bird that lived on Madagascar . The flightless birds , which stood nearly 10 feet ( three metres ) tall and weighted half a tonne , died out in the 17th century after heavy hunting . Scroll down for video . This 12 inch long elephant bird egg - just one of 25 known to remain intact around the world - is going on sale . There are thought to be just 25 preserved intact elephant bird eggs left in existence , with most in museums . Now one owned by a German marine biologist Professor Hubert Caspers , who worked at the Institute for Hydrobiology and Fisheries Science before his death in 1998 , is to go on sale in Bruges , Belgium . Genetic material has been extracted from the shells of ancient elephant bird eggs . It has raised hopes that it may be possible to use cloning techniques to resurrect the extinct species . By injecting the genetic material into the unfertilised eggs of other large flightless birds like the ostrich , it may be possible to recreate the elephant bird . However , scientists face significant challenges that need to be overcome before this is possible . Cloning birds is considered to be particularly challenging . Extracting enough DNA from eggshells is also thought to be another limiting factor . Finally much of the habitat the the elephant birds once inhabited has now changed , so there may be few places where such a large species could now live . Scans taken of the egg , which is at least 400 years old , have also revealed the tiny bones of an embryo that had started to grow inside along with dehydrated organic material . Scientists were recently able to extract DNA from a similar egg , raising hopes that it may be possible to bring the elephant bird back to life using cloning techniques . Auctioneers Rob Michiels , who is selling the egg along with other items from Dr Caspers collection , said the egg appeared to be older than other eggs that have been sold recently . He said : 'The eggs of elephant birds are extremely rare - there are probably 25 of them in the world . 'This once comes from the collection of Dr Caspers and we have been asked to sell it by his children who thought it was a dinosaur egg . 'The children did n't know a lot about their father 's collection . ' I was invited to Hamburg to look at a collection of antique tiles that he owned and I spotted the egg . It was just sat in a box . 'We have had a CT scan of the egg and it showed there is still organic , dehydrated material inside in the form of fetal bones . 'Technically , you could extract DNA from it and if you have a very large ostrich you could re-create a form of an elephant bird . 'The mother either ran away from the nest or was killed . ' A CT scan of the elephant bird egg revealed dehydrated organic matter , shown as pink in the image above , and fragments of fetal bone still preserved inside the egg , shown by the small white mark in the pink material . The egg that has come up for sale ( left ) is one of the largest in the world and was laid by the now extinct elephant bird ( right ) which grew to around ten feet tall and lived in Madagascar until the 17th Century . The elephant bird , or Aepyornis maximus , was one of the largest birds to have ever lived . They are thought to have been common in Madagascar until they wre hunted into extinction during the 17th century . Fossilised egg fragments can still be found on the ground in some parts of Madagascar . David Attenborough , the natural history broadcaster , owns an almost complete eggshell that he pieced together from fragments collected by locals while he filmed Zoo Quest to Madagasar in 1961 . The CT scans took slices through the egg and revealed dehydrated organic material and bone fragments inside . Another elephant bird egg was sold in 2013 for £66,675 - more than twice its expected value . Douglas G. D. Russell , senior curator of birds , eggs and nests at the Natural History Museum in London , said the elephant bird eggs were now very rare . He said : 'The export of their eggs from Madagascar is now strictly forbidden by the country ’ s legislation and complete eggs are relatively rare . 'As a rare , complete egg of an extinct species with some , albeit minimal , foetal bone it is noteworthy and all additional information on this enormous enigmatic bird is exciting . ' Broadcaster David Attenborough is one of the few people to won a giant elephant bird egg after he pieced one together from fragments brought to him by locals while he was filming in Madagascar for the BBC in 1961 . This fossilised elephant bird egg , shown next to a hen 's egg , sold for £66,000 during an auction in 2013 .
The egg , which belonged to a German biologist , has an eight inch diametre . CT scans have revealed dried organic material and bone fragments inside . It is thought to be one of only 25 intact elephant bird eggs left in the world . The egg is expected to sell for more than £50,000 at an auction in Belgium . Elephant birds died out during the 17th century after being heavily hunted .