The discovery of a rare fossil goose in an ancient Central Otago lake shows the evolutionary history of Aotearoa New Zealand birds is much more dynamic than once thought, a University of Otago - Ōtākou Whakaihu Waka researcher says.
Associate Professor Nic Rawlence, Director of the Otago Palaeogenetics Laboratory, is co-author of a new paper which analyses the fossil and its origins.
Published in the journal Historical Biology, the paper is an international collaboration between Otago, the Museum of New Zealand Te Papa Tongarewa, and the University of Cambridge (UK) analysing fossils uncovered around St Bathans.
Associate Professor Rawlence says while many waterfowl species are incredibly common in the fossil deposits in the area, some are quite rare.
The researchers re-examined the remains of all bones previously identified as belonging to geese and compared them to the other waterfowl bones from the deposit and a broad collection of comparative bird skeletons.
"We determined that the bones included an undescribed species, the size of a small goose," he says.
A reconstruction of the St Bathans goose (Metechen luti). Artwork by Sasha Votyakova, © Te Papa CC BY 4.0
The research team named the St Bathans goose Meterchen luti in reference to the nursery rhyme Old Mother Goose, where, in this case, an ancient goose rises out of the mud of a fossil deposit. Meterchen means "mother goose" in ancient Greek, while luti is Latin for "of the mud".
"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."
This, along with other recent genetic research, shows the evolutionary origins of New Zealand's birds is more dynamic than previously thought.
Lead author Alan Tennyson, of Te Papa, says while many species of birds have been arriving throughout geological history, the ancestors of some of our large birds have only arrived here surprisingly recently - in the past four to five million years - including takahē, Forbes' harrier and the giant Haast's eagle.
"An earlier theory argued that the St Bathans goose represented the direct ancestors of giant flightless Cnemiornis geese, implying this lineage had a very long history (of at least 14 million years) in Zealandia," he says.
"However, this conflicts with genetic evidence suggesting the ancestors of Cnemiornis arrived from Australia only about seven million years ago, which proponents of the earlier theory discarded.
"Our rigorous reassessment supports the later arrival theory."
So, while the ancestors of the St Bathans goose arrived in Zealandia prior to 14 million years ago, no descendants survived, Associate Professor Rawlence says.
"Using all the tools in the toolbox, including DNA and fossils, we can reconstruct how the dynamic geological, climatic and human history of Zealandia has shaped the evolution of Aotearoa fauna in ever more detail," he says.
"The relatively recent evolution of the giant flightless Cnemiornis geese offers another striking example of rapid morphological change that can occur within a short timeframe on islands. At one metre tall and weighing up to 18kg, these were the largest geese in the world."
Publication:
Alan J. D. Tennyson, Elizabeth M. Steell, Pascale Lubbe, Amy L. Adams, Liam Greer, Alex H. Brown, Laura J. E. Wilson, Timothy C. Campbell, Tobia C. Dale, Nicolas J. Rawlence
