By Dr Jonathan Cramb, Discovery Centre Information Officer

Identifying obscure and bizarre objects is all in a day’s work for staff in the Queensland Museum Discovery Centre!

What animal laid this enormous egg?

The replica egg is huge! It’s much bigger than any egg laid by any living Australian bird.

The giant egg replica even dwarfs the egg of an Ostrich, which has the largest egg of any living bird.

The Mystery

The Queensland Museum Discovery Centre recently acquired a replica of the largest known egg. The egg is almost 30 centimetres long, and the original fresh egg would have weighed a whopping 12 kilograms! Eggs like this have been found on the coast of Western Australia. What might have laid them? Perhaps a dinosaur?

What is it?

These huge eggs were laid by the extinct elephant birds of Madagascar.

Elephant birds are ratites, a group of mostly flightless birds that also includes emus, ostriches and kiwis. There are several species of elephant birds, and determining exactly which of them laid a particular egg is difficult. The largest eggs are commonly said to be laid by Aepyornis maximus, although they could also be from an even larger species called Vorombe titan. The largest elephant birds are about the same size as the extinct dromornithid birds from Australia, which have been hypothesised to have laid similarly large eggs.

Elephant bird eggs have a larger volume than any known non-avian dinosaur egg. Eggs that are thought to have been laid by a large theropod (similar to Gigantoraptor) are longer, but are sausage-shaped so have a smaller volume. Surprisingly, the approximately spherical eggs of gargantuan sauropod dinosaurs are much smaller, with a diameter of about 12-14 centimetres.

As already mentioned, elephant birds lived in Madagascar, on the other side of the Indian Ocean from Australia, yet elephant bird eggs have been found on the coast in Western Australia (two have been found, one in the 1930s and another in 1992). This raises the question: how did they get here?

It’s actually rather simple, if still quite extraordinary. As any good cook will know, you can determine whether an egg has gone rotten by placing it in a bowl of water. Eggs that have died and started to rot will float. Remarkable as it seems, this means that a rotten elephant bird egg can float across an entire ocean!

Visit the Discovery Centre to see this Mystery of the Month this November. Do you have an interesting question or mystery object? Our helpful and knowledgeable staff can answer your questions through our Ask an Expert inquiry service.