It wasn't the oldest or even—if you can believe it—the largest penguin in Earth's history, but the newly discovered mega-penguin, Kumimanu biceae, is a giant compared to modern birds.
Described this week in the journal Nature Communications, the 60-million-year-old penguin stood at just under 5 feet 9 inches tall and weighed over 220 pounds. It was comparable in size to a solidly built American man. This makes it undeniably one of the most giant fossil penguins, second only to the fragmented fossil Palaeeudyptes klekowskii, a mega-penguin that roamed Antarctica 37 million years ago, reports Rachel Feltman for Popular Science. For comparison, Feltman notes, the largest of the 17 modern penguin species is Emperor Penguin, which stands at just 48 inches tall—roughly the size of a third grader.
Discovered on Hampden Beach south of Christchurch in New Zealand, the fossilized skeleton was so hidden in the surrounding rock that scientists originally mistook it for a turtle, Amina Khan reports for L.A. Times. The team began excavation of the behemoth and found several parts of the skeleton: wing and shoulder bones, leg bones, breastbone and some vertebrate, along with other bone fragments. Though it wasn't the largest, the skeletal fragments suggest that K. biceae had the longest femurs (leg bones) of any penguin.
From its age and physiology, the researchers conclude that K. biceae is one of the first penguin species to evolve, and the oldest yet found of the giant penguins. This suggests that gigantism evolved shortly after penguins lost the ability to fly and took to the water, but later re-emerged millions of years later. As Feltman notes, the other known mega-penguins are tens of millions of years younger than the newly discovered creature.
“Gigantism therefore may be an inherent feature of Paleogene penguins, which may have evolved soon after aerodynamic constraints ceased to exist,” Gerald Mayr of the Senckenberg Research Institute and Natural History Museum Frankfurt and his team wrote in the study.
It’s unclear why penguins got so big. Appearing in the fossil record just a few million years after the extinction of large predatory marine reptiles, K. biceae may have evolved to fill that newly-opened ecological niche, the researchers note in the paper. As Feltman reports, the larger sizes could have given giant penguins a competitive boost in claiming the best breeding grounds, or improved their diving capacities.
Five million years is a very short time for penguins to lose the ability to fly, gain the ability to fly, and grow into mega-penguins, writes Khan. This hints that the penguin lineage might be older than previously thought, and early penguins—themselves descendants of dinosaurs—could have coexisted with non-avian dinosaurs before they went extinct.
Though the massive penguin seems astonishing compared to our modern tuxedo-clad waddlers, Mayer wasn't particularly surprised at the size. “Actually, it is often observed that flightless birds become very large,” he tells Feltman. “One rather has to answer the question why there are no giant penguins today.”