Fossils give us information about the evolution of life, and sometimes that information is quite startling. Recent fossil discoveries from New Zealand have revealed a remarkably diverse collection of Paleocene tribal group penguins.

An international team, including researchers from the University of Cambridge, recently unearthed fossil bones from two newly described penguin species in New Zealand. One of the penguins turns out to be the most gigantic penguin that ever lived.

The fossil suggests the penguin must have been more than three times the size of the largest living penguins, weighing more than 150 kilograms.

The team initially discovered the fossils in 57-million-year-old beach boulders in North Otago, New Zealand’s South Island, between 2016 and 2017. The fossils were then uncovered from within the boulders by Al Manning. According to their age, which is estimated to be between 59.5 and 55.5 million years, they lived between five and 10 million years after the end of the Cretaceous extinction event, which also caused the extinction of non-avian dinosaurs.

The team named the new species Kumimanu fordycei in honor of Dr. R. Ewan Fordyce, Emeritus Professor at the University of Otago. The second penguin species, called Petradyptes stone house, weighs about 50 kg. It turns out to be smaller than Kumimanu fordycei, but still well above the weight of an emperor penguin. The name combines the Greek ‘petra’ for rock and ‘dyptes’ for diver, a pun on the diving bird preserved in a boulder.

Skeletal illustrations
Skeletal illustrations of Kumimanu fordycei, Petradyptes stonehousei and a modern emperor penguin showing the dimensions of the new fossil species. Credits: Dr Simone Giovanardi.

To compare the bones to those of other fossil species, flightless diving birds such as auks and modern-day penguins, the scientists used laser scanners to generate digital models of the bones. The scientists examined hundreds of modern penguin bones to estimate the size of the new species. They then used the dimensions of the bones in the fins to determine weight using a regression analysis.

They concluded that a penguin weighing a whopping 154 kg had the largest fin bones. Emperor penguins, the largest and heaviest living, often weigh between 22 and 45 kg.

These two recently discovered species show that penguins grew in size over millions of years before developing their fin apparatus. The study found that the two species still possessed rudimentary features, such as muscle attachment points similar to those found in flying birds and thinner fin bones.

Dr. Daniel Ksepka of the Bruce Museum in Greenwich, Connecticut, said: “When asked why early penguins grew to gigantic proportions.”

β€œIt made them more efficient in the water. Size brings many benefits. A larger penguin would have been able to catch bigger prey, and more importantly, it would have been better at maintaining body temperature in cold water. It is possible that breaking the 100-pound barrier allowed the earliest penguins to spread from New Zealand to other parts of the world.”

Co-author Dr. Daniel Thomas from Massey University in Auckland said: “If we start looking at these finds not as isolated bones, but as parts of a whole living animal, then a picture begins to form. Large, warm-blooded marine animals living today can dive to great depths. This raises questions about whether Kumimanu fordycei had an ecology that penguins do not have today, being able to reach deeper waters and find food inaccessible to living penguins.”

Dr. Daniel Field from Cambridge’s Department of Earth Sciences said: “Kumimanu fordycei is said to have been an extremely amazing sight on the beaches of New Zealand 57 million years ago, and the combination of its massive size and the incomplete nature of its fossil remains make it one of the most intriguing fossil birds ever found. Hopefully, future fossil discoveries will shed more light on the biology of this amazing early penguin.”

Magazine reference:

  1. Daniel T. Ksepka et al. ‘Largest known fossil penguin provides insight into early evolution of sphenisciform body size and fin anatomy.’ Journal of Paleontology (2023). DOI: 10.1017/jpa.2022.88