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Scientists say a newly described goose fossil, recovered from ancient lake sediments in Central Otago, is prompting a fresh look at the evolution of New Zealand's distinctive birdlife.
Although the animal itself was only about the size of a small goose, the find feeds into a broader debate over Aotearoa's avian past, including how fast birds on islands can evolve into very different forms.
What happened?
According to ScienceDaily, the research team (from the University of Otago, the Museum of New Zealand Te Papa Tongarewa, and the University of Cambridge) concluded that fossils from the St Bathans deposits are a goose species that hadn't been formally described before.
In Historical Biology, the authors report on bones recovered from the Central Otago lake-bed deposits. Co-author Associate Professor Nic Rawlence of the University of Otago said that, even though St Bathans has yielded many waterfowl fossils, goose material there is comparatively uncommon.
The team tested that identification by going back through bones that earlier work had classified as geese.
"We determined that the bones included an undescribed species, the size of a small goose," Rawlence said.
Researchers named the species Meterchen luti, a reference to the nursery rhyme "Old Mother Goose."
Why does it matter?
The finding weakens a longstanding explanation for the origins of some famous New Zealand birds.
Under that earlier view, the St Bathans bird was thought to sit directly in the line that later produced the giant, flightless Cnemiornis geese of New Zealand.
Lead author Alan Tennyson of the Museum of New Zealand Te Papa Tongarewa said the timing is the key problem: the older hypothesis would require the lineage to have been in Zealandia for 14 million years or longer. However, he explained, "This conflicts with genetic evidence suggesting the ancestors of Cnemiornis arrived from Australia only about seven million years ago."
Taken together, the fossil and genetic evidence point to a bird history in New Zealand that involved more turnover and faster change than scientists once assumed. It helps explain why island ecosystems can produce such unusual species and why those same ecosystems can be especially vulnerable to disruption and extinction.
What's being done?
Scientists are still learning from fossils already held in collections.
By reassessing bones already assigned to geese and comparing them with fresh evidence, the team is working to clarify where this bird fits on the evolutionary tree, building on a recent fossil find in a Waitomo cave that similarly reshaped scientists' understanding of New Zealand's ancient birdlife.
According to Rawlence, the St Bathans goose "is not closely related to the recently-extinct giant flightless New Zealand geese (Cnemiornis species) or their Australian cousin, the Cape Barren goose."
That finding helps bring the fossil evidence into better alignment with genetic research and gives scientists a clearer timeline for how major bird groups reached and adapted to New Zealand.
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