This morning, a team of scientists unveiled the Crossvallia waiparensis: a 1.6m-tall penguin from the Paleocene Epoch, between 66 and 56 million years ago. Image / Canterbury Museum
Giant parrots, giant bats, giant eagles and giant penguins.
New Zealand is well known for its strange and long-lost creatures that reached huge sizes in our prehistoric wilderness - and the likely evolutionary drivers have varied.
Among them: a remote and isolated ecosystem, a lack of predators or competition, and what one palaeoecologist likened to a "job vacancy" that needed filling.
THE GIANT PENGUIN
This morning, a team of scientists unveiled the Crossvallia waiparensis: a 1.6m-tall penguin from the Paleocene Epoch, between 66 and 56 million years ago.
Identified from fossils found at Waipara Greensand, a fossil treasure trove in North Canterbury, the species was one of the world's oldest known penguin species.
It was also one of the largest – taller even than today's 1.2 metre Emperor Penguin, and weighing up to 70 to 80 kg.
The second such specimen traced back to the same epoch, the find seemed to offer further evidence that these ancient penguins were not only huge, but grew super-sized very early in their evolution.
One of the scientists behind the discovery, Canterbury Museum senior curator Professor Paul Scofield, suspected their growth might have been partly due to the demise of dinosaurs and marine reptiles.
"There's something known as mesopredator release, where you get rid of a bunch of apex predators, and there's a hole in the ecosystem and something comes along to fill it," Scofield said.
Enter, Crossvallia waiparensis.
Their growth was likely also helped by there being nothing around to eat them.
In any case, Scofield and colleagues were starting to realise there were likely two eras of giant penguins: one which existed at the time of this monster, and another that lasted from the Eocene and into Oligocene, which began about 33 million years ago.
Neither lasted.
"I like to think of these gigantic penguins as failed evolutionary experiments – and they even had two goes at it."
THE GIANT PARROT
Today's big reveal came days after researchers revealed a super-sized giant parrot that once stood half the height of a human.
Analysis of leg bones believed to be 20 million years old led to the identification of what was believed to be the biggest parrot species, suitably dubbed "Hercules the Unexpected".
Scofield pointed out there wasn't any reason to compare the penguin and the parrot - the former a marine species that was about when New Zealand hadn't fully broken apart from ancient southern supercontinent Gondwana, and the latter, a terrestrial bird that proved a classic case of "island gigantism" that occurred in isolation.
Scientists who found large strange bones near an old gold mining town in Otago first thought it could be a duck.
There was no other parrot so big anywhere else in the fossil history of the world - filling the same niche at the top of the fruit-eating hierarchy that was filled by the extinct dodo, a kind of pigeon, in Mauritius.
"On all islands there is only one large herbivore/omnivore on the ground," said Dr Trevor Worthy, who has led analysis of fossil bones at the famed St Bathans site for 20 years.
There was the dodo in Mauritius, another giant pigeon in Viti Levu in Fiji, and a set of large ducks in Hawaii - but no pigeons or parrots.
"Generally there is only one kind of thing that made the niche. It's probably first in, first served."
But Otago University's Dr Nic Rawlence was still puzzled by the parrot's size.
"A giant penguin makes sense. But a giant parrot the size of my three-year-old? That's just weird."
Like Worthy, he suspected that Hercules had some form of job vacancy to fill.
Like the penguin's, the parrot's reign didn't last: a big cooling in the world's climate which lowered temperatures by about 8C about 12 million years ago wiped out Otago's subtropical forests and drastically reduced the bird species that had grown fat on their fruit.
THE GIANT BAT
The St Bathans site was also where scientists recently unearthed fossil remains of a giant, burrowing bat that was three times the size of the average bat today.
The extinct creature, which weighed about 40g, represented the largest burrowing bat known to science, and New Zealand's first new bat genus for more than 150 years.
Teeth and bones of the bat were recovered from sediments dated between 16 and 19 million years old.
Burrowing bats, now found only in New Zealand, were peculiar because they not only fly, but also scurry about on all fours over the forest floor, under leaf litter and along tree branches.
It was named Vulcanops jennyworthyae, after Jenny Worthy, who was part of the team that found the fossils, and after Vulcan, the mythological Roman god of fire and volcanoes, in reference to New Zealand's tectonic nature, but also to St Bathans' historic Vulcan Hotel.
The bats were related to vampire bats, ghost-faced bats, fishing and frog-eating bats, and nectar-feeding bats, and belong to a bat superfamily that once spanned the southern landmasses of Australia, New Zealand, South America and possibly Antarctica.
Around 50 million years ago, these landmasses were connected as the last vestiges of Gondwana.
Again, Rawlence said, it was a case of island gigantism.
"It doesn't always mean you have to be huge – just the biggest example on an island ecosystem. I'd even call the kakapo a giant."
Amongst other extinct examples: the adzebill, the moa, the New Zealand swan or pouwa, the Eyles' harrier - and the Haast's eagle.
THE GIANT EAGLE
With a wingspan reaching as wide as 3m and huge claws that could crush bone, the Haast's eagle was one of the most fearsome creatures ever to stalk New Zealand's prehistoric wilderness.
The largest eagle known to have existed anywhere, its demise quickly followed that of its much-larger prey, the moa, which was hunted to extinction by early Maori settlers around 1400AD.
Researchers have theorised the feathered killing machine used its large beak to rip into the internal organs of its prey, whose death would later come from blood loss.
Studies have suggested the bird diverged from the much smaller little eagle and booted eagle as recently as 1.8 million to 700,000 years ago – potentially increasing in weight by ten to 15 times.
As Otago University biological anthropologist Dr Michael Knapp explained, there were no other native land mammals around in New Zealand's prehistoric wilderness, save for two species of bats.
"There was nothing that preyed on the large birds like the multiple species of moa that called New Zealand their home," Knapp said.
"Therefore, being able to kill larger prey was a selective advantage for birds of prey. There was simply more food available in the 'large' size range, than among smaller animals that were already preyed upon by other species."
Therefore, the bigger an individual eagle was, the better its chances to kill larger prey and the better its chances to look big and healthy when it came to finding a partner.
Rawlence pointed out that the moa, too, had sprung from small flying birds that arrived here about 58 million years ago.
"When the ancestors of kiwi arrived in New Zealand, about 50 million years ago, the job vacancy for a big giant bird was already filled by moa, so they had to stay small."
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