Last updated December 13, 2019 at 11:32 am
We love giant penguins – but this ancient penguin is when they started to get small.
Why This Matters: K. Stilwelli is a crucial piece in the penguin evolution puzzle.
What waddled on land but swam quickly in subtropical seas more than 60 million years ago, after the dinosaurs were wiped out on sea and land?
Fossil records show giant human-sized penguins zipped through Southern Hemisphere waters – alongside smaller forms, similar in size to some species that live in Antarctica today.
Now the newly described Kupoupou stilwelli has been found on the geographically remote Chatham Islands in the southern Pacific near New Zealand’s South Island. It appears to be the oldest penguin known with proportions close to its modern relatives.
Bridging the gap between giant penguins and their modern relatives
It lived between 62.5 million and 60 million years ago at a time when there was no ice cap at the South Pole and the seas around New Zealand were tropical or subtropical.
Jacob Blokland from Flinders University made the discovery after studying fossil skeletons collected from Chatham Island between 2006 and 2011.
He helped build a picture of an ancient penguin that bridges a gap between extinct giant penguins and their modern relatives.
“Next to its colossal human-sized cousins, including the recently described monster penguin Crossvallia waiparensis, Kupoupou was comparatively small – no bigger than modern King Penguins which stand just under 1.1 metres tall,” says Blokland, who worked with Flinders palaeontologist Trevor Worthy and Paul Scofield and Catherine Reid from the University of Canterbury on the discovery.
“Kupoupou also had proportionally shorter legs than some other early fossil penguins. In this respect, it was more like the penguins of today, meaning it would have waddled on land,” he says.
“This penguin is the first that has modern proportions both in terms of its size and in its hind limb and foot bones (the tarsometatarsus) or foot shape.”
Penguins rapidly evolved
As published in the US journal Palaeontologica Electronica, the animal’s scientific name acknowledges the Indigenous Moriori people of the Chatham Island (Rēkohu), with Kupoupou meaning ‘diving bird’ in Te Re Moriori.
The discovery may even link the origins of penguins themselves to the eastern region of New Zealand – from the Chatham Island archipelago to the eastern coast of the South Island, where other most ancient penguin fossils have been found, 800km away.
Professor Scofield, says the paper provides further support for the theory that penguins rapidly evolved shortly after the period when dinosaurs still walked the land and giant marine reptiles swam in the sea.
“We think it’s likely that the ancestors of penguins diverged from the lineage leading to their closest living relatives – such as albatross and petrels – during the Late Cretaceous period, and then many different species sprang up after the dinosaurs were wiped out,” Scofield says.
“It’s not impossible that penguins lost the ability to fly and gained the ability to swim after the extinction event of 66 million years ago, implying the birds underwent huge changes in a very short time. If we ever find a penguin fossil from the Cretaceous period, we’ll know for sure.”