From the Heritage Auctions website:
RARE COMPLETE "GREAT ELEPHANT BIRD EGG" WITH UNIQUE EMBRYONIC BONES
This incredible egg is from the largest bird ever to have lived: the Great Elephant Bird of Madagascar. The Aepyornis was a ratite (flightless bird), like the Moa, the Rhea, or the Ostrich; lacking the keel to its breastbone that would provide sufficient leverage to operate its wings in flight. Believed to have grown to over 10 feet tall and weighing close to 900 pounds, it was a native of Madagascar that survived at least until the late 17th Century; the French governor of the island at that time wrote of a reclusive giant bird that laid its eggs in hidden places. Indeed, human desire for these eggs may have been the cause of its extinction as shell fragments have been found amongst remains of human-made fires; suggesting that they were a substantial food source. The bird has also been popular in folk legend; supposedly inspiring the Roc, or Rukh, of Marco Polo's writings and of the Thousand and One Nights; and immortalized by H.G. Wells in his story "Aepyornis Island" in 1898. Remarkably little is known about the creature because no complete skeleton has ever been discovered and very few associated ones are available for study; their most common remains are these incredible eggs; with a volume approximately 170 times that of a chicken egg. Most common are reconstructed eggs from fragments, but occasionally a complete specimen is discovered such as the one presented here. So rare in fact that there are fewer than 30 complete specimens that have been documented and preserved in museum collectionsThe present example is considerably more significant than that, however. Because intact undamaged eggs are so scarce, scientists have been universally unwilling to break them open to examine the embryonic contents. It was only in recent years that X-ray technology was used to look inside the complete egg of the National Geographic Society collection in Washington D.C. and a detailed study compiled on its contents. The present egg, however, was accidentally dropped a number of years ago, which turned out to be an incredibly fortunate accident; out tumbled the perfectly preserved bones of an embryonic Aepyornis: a totally unique specimen. The egg was expertly repaired and the contents kept separate. Included in this lot are the complete contents of this egg which includes approximately 75% of the embryonic skeleton organized into a number of plastic containers. Several bones of note include large thick limb bones and significant skull elements including a part of the upper beak. The egg itself shows almost no sign of its past damage, remaining in excellent condition with a wonderful shell texture. The egg measures 12 ½ inches long and 28 inches in circumference; a unique, fascinating, and highly significant specimen.