Ancient fossils found between two layers of volcanic ash reveal a million-year-old mystery hiding beneath New Zealand.
On the North Island of New Zealand, there is a limestone cave with a name that hints at what it once contained: Moa Eggshell Cave. The name comes from the fragments of enormous eggs scattered on its floor, remnants of the giant flightless birds that roamed the islands until a few hundred years ago.
But when a team of scientists entered the cave recently, they found something far older beneath their feet. In the layers of sediment, sandwiched between two distinct bands of volcanic ash, lay the bones of creatures that had been dead for more than a million years. The ash had preserved them in place, a snapshot of a forest that existed long before humans ever reached the shores of New Zealand.
The fossils the team pulled from that cave represent 12 species of ancient birds and four species of extinct frogs. Several of the bird species were previously unknown to science. The find is so significant that researchers are calling it not a missing chapter in the natural history of New Zealand, but a missing volume.
A Million Years Trapped Between Two Eruptions
The ash layers that sealed the fossils came from two major volcanic eruptions. The first occurred 1.55 million years ago, blanketing the landscape and preserving whatever lay beneath. The second eruption, 1 million years ago, laid down another layer on top. The bones found between them offer a rare window into a specific moment in time roughly 1 to 1.5 million years ago, a period that has long been a blank spot in the fossil record.
Trevor Worthy, associate professor at Flinders University and lead author of the study published in the Journal of Palaeontology, said the discovery reveals a completely unrecognized ancient fauna. “This is a newly recognized avifauna for New Zealand,” Worthy said. “This remarkable find suggests our ancient forests were once home to a diverse group of birds that did not survive the next million years.”
By the time humans arrived in New Zealand around 750 years ago, many of these species were already gone. The researchers estimate that between 33 and 50 percent of all species on the North Island went extinct during the million years before human contact. The likely causes were rapid climate shifts and catastrophic volcanic eruptions that repeatedly reshaped the landscape.
A Parrot Ancestor That Might Have Flown
Among the most striking discoveries was a new species of parrot named Strigops insulaborealis. It is an ancient relative of the modern kākāpō, the large, flightless, nocturnal parrot that has become a symbol of New Zealand’s unique wildlife and a focus of intensive conservation efforts.
The modern kākāpō has powerful, muscular legs built for climbing trees and covering ground on foot. Its newly discovered ancestor had weaker legs, suggesting it was not as skilled a climber. The difference in bone structure raises the possibility that Strigops insulaborealis could fly, unlike its grounded descendant. As detailed in a report on the discovery from Discover Wildlife, the researchers caution that more study is needed to confirm whether flight was possible, but the implication alone shifts the understanding of how the kākāpō lineage evolved.
Paul Scofield, senior curator of natural history at Canterbury Museum and study co author, said the shifting environment likely forced repeated resets of the bird populations. “The shifting forest and shrubland habitats forced a reset of the bird populations,” Scofield said. “We believe this was a major driver for the evolutionary diversification of birds and other fauna in the North Island.”
The cave also contained the remains of an extinct ancestor of the modern takahē, another flightless bird that survives today only through intensive management. Another find was an extinct species of pigeon closely related to the Australian bronzewing pigeons, a group not previously known to have lived in New Zealand.
The Missing Volume in New Zealand’s History
Scientists already had a reasonably clear picture of New Zealand’s wildlife from about 20 million years ago, thanks to fossil deposits at other sites. They also knew the recent past, the last thousand years or so, from bones found in caves and dunes. But the long stretch in between had yielded almost nothing.
Scofield described the gap in stark terms. “This wasn’t a missing chapter in New Zealand’s ancient history,” he said. “It was a missing volume.”
The fossils from Moa Eggshell Cave fill that gap. They show that the forests of the North Island once supported a different set of species than the ones that greeted the first Polynesian settlers. According to coverage from Popular Mechanics on the cave exploration, those earlier species died out not because of hunting or habitat destruction by people, but because the land itself kept changing beneath them. Volcanoes erupted. Forests burned or were buried. Climate swung between warmer and cooler periods. Each time, some species vanished and new ones evolved to take their place.
Worthy said the finding shifts the way scientists think about extinction in New Zealand. “For decades, the extinction of New Zealand’s birds was viewed primarily through the lens of human arrival 750 years ago,” Worthy said. “This study proves that natural forces like super volcanoes and dramatic climate shifts were already sculpting the unique identity of our wildlife over a million years ago.”
A Record Preserved by Chance
The preservation of the fossils depended on a specific sequence of events. The cave provided shelter from the elements. The ash layers from two different eruptions sealed the sediment in place, protecting it from disturbance. Without that volcanic overprint, the bones would likely have crumbled or washed away long ago.
The researchers identified the fossils by comparing them with known specimens from other sites. The work required distinguishing between species that lived a million years apart but sometimes looked similar in bone structure. The extinct pigeon, for example, had to be separated from modern pigeon bones and from other extinct species found elsewhere in the country.
The discovery also opens new questions. If so many species went extinct before humans arrived, what did the forests look like when the first people stepped ashore? The birds they encountered were already the survivors of a long history of volcanic upheaval and climate shifts. The moa and the kākāpō they saw were the latest versions of lineages that had been reshuffled repeatedly over millions of years.
NOTE – This article was originally published in Indian Defence Review and can be viewed here
