It’s hard to believe that anything small thrived during the time of the dinosaurs, but according to new fossils found in Central Otago in New Zealand, miniscule flightless birds survived the dinosaur-ruled prehistoric era.
A team from Flinders University discovered the bones of tiny flightless ‘rail’ birds in 19 million-year-old lake sediments in Central Otago. The study, by researchers from Australia and NZ, is published in the Journal of Systematic Palaeontology.
When humans first came to New Zealand there would have been many flightless birds still inhabiting the island. Notably the moa, several kiwi, two huge geese, two adzebills, even some tiny wrens, and at least five flightless rails.However, the rail, which was of a similar size to a sparrow, died out soon after human intervention.
At that time, a 5,600 km2 mega-lake dominated the landscape of NZ’s South Island. It was surrounded by a subtropical rainforest. Plants typical of Australia and long lost from NZ, such as eucalypts, casuarinas, palms and cycads, would have surrounded the lake. An ideal habitat for the flightless rails during the time.
“Flightlessness in birds is often associated with an increase in size,” says Flinders University PhD Ellen Mather, the study’s lead author.
“The weka, which is in the same family as our fossil birds and lives in New Zealand today, is about the size of a chicken. The Banded Rail, their closest flying relative, is about half that size.”
The new species is so different to any rails previously discovered that their closest relatives and origin remains a mystery.
“The ongoing research into the fossil birds of New Zealand builds on that begun over 150 years ago. It continues to throw up revelations into the timing and origins of major groups of birds that characterize modern avifaunas,” said Associate Professor Trevor Worthy of Flinders University.
“Charting how lineages like these rails have changed through time on an island that has been geographically isolated for over 80 million years will test basic presumptions made about bird evolution in general,” Professor Archer says.
The rails discovered in New Zealand are thought to be the oldest flightless birds discovered globally.
Lead image: A tiny extinct rail (30-40g) is overshadowed by a regular duck. Artist's impression courtesy Gavin Mouldey