An artistic reconstruction of Kumimanu biceae in size comparison to a human diver. Reconstruction by G. Mayr/Senckenberg Research Institute

When people think of penguins, their minds usually drift all the way down to the South Pole. But there’s a spheniscid hotspot to be found on the way there. Thirteen of the world’s 18 penguin species have been recorded around New Zealand and its waters. Nine breed there; three have made it their permanent home. None of these penguins, however, even approach the size of their recently discovered ancestor, Kumimanu biceae, whose fossil was found a few years ago at Hampden Beach, in the South Island’s Otago region.

K. biceae wasn’t just a whopper of a penguin—it was likely the largest one that ever lived. Its fossil has been dated to the late Paleocene epoch, sometime between 55.5.and 59.5 million years ago. Standing nearly six feet tall, and weighing around 220 pounds, it was around 33 times the size of the Little Blue Penguin, its strikingly cute descendent. Even the world’s largest living penguin, the majestic Emperor Penguin, would have been dwarfed by this colossal bird.

Many millions of years ago, the seas were full of large, predatory marine reptiles. When they died out, in the early years of the period sometimes referred to as the Age of Mammals, a number of giant penguins evolved to take their place. This seems to have happened shortly after the birds became flightless divers—meaning K. biceae once went whizzing through the waters of the South Pacific, gobbling fish after fish as it went.

So, why don’t we find mind-bogglingly large penguins waddling up and down the beaches of New Zealand today? The answer is in the water, researchers say. Around 33 million years ago, large marine mammals like tusked dolphins, whales, and seals—all of which had a hefty appetite for seafood—began to populate the world’s oceans. Faced with the competition, penguin species got smaller, or died out altogether. Sad news for bird lovers—but probably quite a relief for the fish.