In December 2017, the science journal “Nature Communications” published a description of a newly discovered species of prehistoric penguin that lived on what is now New Zealand 60 million years ago. Scientists called it Kumimanu biceae, and it stood 1.77 meters (5 feet 10 inches) tall. In other words, it could look the average man in the eye. It also may have weighed as much as 220 pounds.
K. bicae wasn’t the biggest prehistoric penguin, however. That distinction belongs to a behemoth that roamed Antarctica 37 million years ago – and stood six feet eight inches tall, making it as tall as some basketball players.
Gerald Mayr of the Senckenberg Research Institute and Natural History Museum Frankfurt, who was an author of the study, pointed out that it’s not a surprise that some penguins grew quite large. He noted that flightless birds, in general, can become very large. In fact, he believes that it’s more surprising that there aren’t any giant penguins now.
Seventeen penguin species currently roam the Earth. The aptly-named Little Penguin, which lives in New Zealand, is the smallest at just 13 inches tall. The Emperor Penguin is the largest living penguin and stands around four feet tall. That’s a fair-sized bird, but it’s still only about as tall as a third-grade child.
In addition to being big, K. bicae was one of the oldest penguins so far found; it appeared just five million years after the extinction event at the end of the Cretaceous that wiped out the non-avian dinosaurs. K. bicae was also the oldest known giant penguin; the other species developed tens of millions years later. Some of those giant penguins had relatives that were significantly smaller. Mayr commented that gigantism in penguins developed early and appeared many times.
The Cretaceous extinction event had opened up many ecological niches. During the first few million years, small animals throve. As the Earth recovered, some species grew larger and increasingly diverse.
Mayr speculated that giant penguins were outcompeted by marine mammals like whales and seals. He noted that the extinctions of giant penguins seem to have roughly correlated with the growing diversity of marine mammals. He suspected that a combination of competition for food or breeding areas plus outright predation led to the demise of the biggest penguin species.
Mayr and his colleagues still aren’t sure when penguins made the switch from flying to diving and swimming. K. bicae had the anatomy of a diver rather than a flyer, and it was already flightless. While scientists can say that flightlessness appeared early in penguin evolution, they can’t say exactly when. Nor do they know how it happened or what caused penguins to lose their flight capabilities.