Christie's specialist James Hyslop holds a chicken egg (L) next to a pre-17th century, sub-fossilised Elephant Bird egg in London on March 27. The rare egg is expected to sell for 20,000-30,000 GB pounds  ($30,000-45,000) when is it auctioned in London on April 24. The extinct Elephant Bird, a native of Madagascar, was a large bird measuring around 11 feet in height. Reuters/Suzanne Plunkett