Australasian Science: Australia's authority on science since 1938

An Ancient Case of Mistaken Identity?

Credit: Peter Trusler

An image of a pair of Dromornis mihirungs to illustrate their enormous bills and great differences from waterfowl that these browsing herbivores show. Credit: Peter Trusler

By Trevor Worthy

The megafaunal bird Genyornis was six times larger than an emu. Why, then, was its egg the same size? Or was it?

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Mihirungs are extinct giant birds of Australia. The smallest was about the size of an emu and the largest, the 9–7-million-year-old Dromornis stirtoni, is more than ten times the mass of an emu at an amazing 480 kg.

Until the 1990s, these birds were thought to be ratites, somehow related to the emu and cassowary. Since then, however, scientists have classified them among fowl (chickens, ducks and their kin), but it seems they are not close to any of the living forms.

Eight species of mihirungs lived in Australia during the last 26 million years, and while up to three occurred together in the Miocene, only one was left by the Pleistocene. This was Genyornis newtoni, and it’s one of the best-known species. It was discovered in the 1890s in Lake Callabonna, South Australia. From those excavations and others since, dozens of bones of it are known yet it remains rare. We do not even have a reasonable skull to know what shape its head was. Furthermore, while it is of Pleistocene age, all of the sites its bones have been recovered in are either undated or poorly dated, so they tell us little about when exactly this megafaunal bird went extinct.

This problem was thought to have been addressed by an analysis of eggshell that differed from that of emu and was first attributed to Genyornis newtoni in 1981. This kind of eggshell is widespread in sand dunes in...

The full text of this article can be purchased from Informit.