A team of researchers from the Canterbury Museum discovered Crossvallia waiparensis after studying fossils found in Waipara, near the city of Christchurch on New Zealand's south island, according to a press release.
The giant penguin, which stood 1.6 meters (5 feet 3 inches) tall, is the latest member of a growing cast of massive fauna that used to call the island nation home. These include the world's biggest parrot, a giant eagle, a giant burrowing bat, and the moa, a kind of large flightless bird.
At 70-80 kilograms (154-176lb), the penguin would have weighed more than the world's average human being, who tips the scales at 62 kilograms (137lb) according to a 2012 BMC Public Health study.
It lived between 66 and 56 million years ago, during the Paleocene Epoch, making it one of the world's oldest known penguin species.
The largest living penguin species is the Emperor Penguin, which stands 1.2 meters tall.
Amateur paleontologist Leigh Love discovered the giant penguin bones in 2018, and they were analyzed by a team from the Canterbury Museum and the Senckenberg Natural History Museum in Frankfurt, Germany.
According to researchers, the giant penguin's closest relative is another Paleocene species, Crossvallia unienwillia, and this second discovery provides further evidence that early penguins were massive.
"It further reinforces our theory that penguins attained a giant size very early in their evolution," said Vanesa De Pietri of the Canterbury Museum.
The fossilized remains of Crossvallia unienwillia were found in Antarctica, and researchers say the discovery provides evidence of a close connection between New Zealand and Antarctica.
"When the Crossvallia species were alive, New Zealand and Antarctica were very different from today -- Antarctica was covered in forest and both had much warmer climates," said Paul Scofield of the Canterbury Museum.
Both species have leg bones that make researchers think their feet were more important in swimming than those of modern penguins, or standing upright was not yet as important.
More details of the research were published in the journal Alcheringa: An Australasian Journal of Palaeontology.
In early August the Canterbury Museum also revealed details of the world's largest parrot, which used its massive beak to crack open food.
The parrot stood over 3 feet tall and weighed about 15.5 pounds, according to a study. It lived in New Zealand about 19 million years ago.