An international team, including researchers from the University of Cambridge, reported the discovery in the Journal of Paleontology. The paper’s senior author, Alan Tennyson from the Museum of New Zealand Te Papa Tongarewa, discovered the fossils in 57 million-year-old beach boulders in North Otago, on New Zealand’s South Island, between 2016 and 2017.
Experts used laser scanners to create digital models of the bones and compare them to other fossil species, flying diving birds like auks, and modern penguins.
To estimate the size of the new species, the team measured hundreds of modern penguin bones and calculated a regression using flipper bone dimensions to predict weight.
They concluded that the largest flipper bones belong to a penguin that tipped the scales at an astounding 154 kg. In comparison, emperor penguins, the tallest and heaviest of all living penguins, typically weigh between 22 and 45 kg.
“Many early fossil penguins attained enormous sizes, easily dwarfing the largest penguins alive today. Our new species, Kumimanu fordycei, is the largest fossil penguin ever discovered—at approximately 350 pounds, it would have weighed more than [basketball player] Shaquille O’Neal at the peak of his dominance!”
Multiple specimens of a second penguin species were also found, providing a detailed view of the skeleton.
Dubbed Petradyptes stonehousei, it weighed in at 50kg, smaller than Kumimanu fordycei but still well above the weight of an emperor penguin.
These two newly-described species show that penguins got very large early in their evolutionary history, millions of years before they fine-tuned their flipper apparatus.