Mike Safey remembers the summer day in 2006 when he took a group of school children fossil hunting in Kawhia Harbour on the west coast of New Zealand's North Island.
"We paddled across to where the fossils were, and started looking, then quite a number of kids and a few of the adults saw this thing on the foreshore," said Mr Safey, president of the Hamilton Junior Naturalist Club.
"It was just set into the mudstone below the high tide mark."
Mr Safey called over Chris Templer, the club's fossil expert, to take a look.
"He said, 'Crikey, this is something important!'"
Fifteen years later, it turns out the fossil was a new species of giant penguin that stood about 1.4 metres tall and swam in the seas off Zealandia about 30 million years ago.
A detailed analysis of the giant penguin, dubbed Kairuku waewaeroa, has been published in the Journal of Vertebrate Paleontology.
"It's been a long journey of discovery to find out what this thing was," Mr Safey said.
"We long suspected, just because of the sheer size of it ... it was going to be something different."
Long legs gives penguin fossil a name
The new fossil is a close relative of extinct giant penguins previously discovered in New Zealand, said Daniel Thomas, a co-author of the study from Massey University.
"It's not unusual to find giant fossil penguins in New Zealand, but mostly they've come from the South Island," Dr Thomas said.
This is the most complete fossil from the North Island, and one feature in particular sets this big bird apart.
"Waewaeroa is the name we've given it, which is Te reo Maori for 'long legs','' Dr Massey said.
"When we line this up against the other giants, this one actually has these relatively long legs.
"This is the distinguishing feature that we see straight away."
The fossil is beautifully preserved, in part due to the fast actions of Mr Safey and the other members of his club.
"We just happen to have been there when it was freshly exposed by the erosion, but before it had completely disintegrated."
After first discovering the fossil, the group returned a few months later to cut it out of the rocks.
"If we'd left it much longer, the thing would've disintegrated with the elements," Mr Safey said.
"Even in the months between when we first saw it and when we picked it up, it had noticeably deteriorated."
But getting the fossils out of the rocks was a challenge, he said.
"We only had a few hours while the tide was out to get this thing out.
"What amazed us was how intact this fossil was."
After a hard day's work, the team ferried the block of rock containing the fossil on a boat back across the harbour.
Mr Templer continued working on the fossil before it was donated to the Waikato Museum for safekeeping.
"We are incredibly grateful to the Hamilton Junior Naturalist Club that discovered it, collected it, and have been looking after it," Dr Thomas said.
Penguin lived in a different world
To work out what it was, the researchers used 3D scanning to get fine details of all the bones and compared this against a digital library of other penguin fossils, as well as skeletons of living penguins, to see where it fit in the family tree.
"Whenever we see some shift in body proportions like this, we immediately think, 'was there something interesting about the ecology of [where this penguin was living],'" Dr Thomas said.
Today the area is a tidal harbour with grey mudstone cliffs.
"If we walk back to the time of this penguin 30-plus million years ago, this entire area was under water," Dr Thomas said.
Back then, a landmass known as Zealandia was drifting north after splitting from the supercontinent Gondwana.
"This fossil penguin is from a time when most of Zealandia [was] submerged, so this land, we are finding it now was actually the sea floor 35 million years ago and reasonably deep water as well," Dr Thomas said.
While it may not be the first big penguin fossil discovered in New Zealand, the most intact giant penguin fossil on the North Island is still an important find, Dr Thomas added.
"What this represents is a new, potentially rich area for us to start exploring."
And maybe the Hamilton Junior Naturalist Club will make the next big discovery.
"What we tell kids is, 'when you're out, keep your eyes open because there's always new stuff appearing, and there may be things in areas you don't always expect'," Mr Safey said.
"Keep your eyes on the ground and eventually you'll find it, because a lot of these things have been found by amateurs over the years."