Largest penguin that ever lived was a ‘monster bird’ – 02/10/2023 – Science

New Zealand has been a land bird haven for eons. The absence of terrestrial predators has allowed flightless parrots, kiwis and moas to thrive. Now researchers are adding two prehistoric penguins to that aviary.

One species is a muscular giant that roamed the coast of New Zealand about 60 million years ago. At nearly 160 kilograms, it weighed as much as an adult gorilla and is the heaviest penguin known to science.

Alan Tennyson, a paleontologist at the Te Papa Tongarewa Museum of New Zealand, discovered the massive seabird bones in 2017. They were deposited on a beach known for the Moeraki Rocks, which are large cannonball-shaped concretions. Tidal churning broke apart several of these 57-million-year-old rocks, revealing bits of fossilized bone within.

Tennyson and his colleagues identified the fossilized remains of two large penguins. The humerus of one, almost 25 centimeters long, was almost twice the size of those found in emperor penguins, the largest living penguin. In other cliffs were bones of a smaller, more complete species of penguin, which also appeared to be larger than a modern emperor penguin.

The researchers described the ancient birds last Wednesday (8) in the Journal of Paleontology. They named the bigger penguin Kumimanu (a mixture of the Maori words for “monster” and “bird”) fordycei, and the smallest of Petradyptes (“stone diver”) stonehousei.

By creating 3D models of kumimanu’s huge humerus bone and comparing its size and shape to the fin bones of prehistoric and modern penguins, the researchers calculated that the “monster bird” weighed a staggering 154 kg —6.8 kg more than Lane Johnson, the starting forward for the Philadelphia Eagles in the Super Bowl.

According to Daniel Ksepka, a paleontologist at the Bruce Museum in Greenwich, Connecticut, and author of the new study, the fragmented skeleton of kumimanu makes it difficult to pinpoint its height. Ksepka estimates him to be around 1.55 meters, giving him a stocky build. Petradyptes wasn’t a lightweight either. It weighed 49.5 kg, making it heavier than modern emperor penguins, which weigh in at 39.6 kg.

Kumimanu and petradyptes plied New Zealand waters during a sweet spot in oceanic history, according to Ksepka. The asteroid impact that ended the age of dinosaurs wiped out most marine reptiles while the ancestors of seals and whales were still on land. So there were few things that would bother a bear-sized penguin.

“If you’re a little one-pound penguin, a seagull can just rip your head off,” Ksepka said. “But a 300-pound penguin isn’t going to worry about a seagull landing nearby because it would just squash it.”

Despite their prodigious size, kumimanu and petradyptes possessed primitive flippers reminiscent of modern seabirds, such as the auk and puffin, which fly and dive.

Julia Clarke, a paleontologist at the University of Texas at Austin who studies the evolution of bird diving and was not involved in the new study, said it would make sense for early penguins like kumimanu and petradyptes to retain several traits left over from their flying ancestors.

The new species provide further evidence that prehistoric penguins became massive before adapting their flippers into paddle-like appendages. Heavier seabirds are able to dive deeper and longer than their lighter counterparts, Ksepka said. The extra belly would also have helped these penguins stay warm in the water.

Although the kumimanu was powerful, it did not outperform its smaller penguin cousins. “You have super-large penguins eating the biggest prey, and you have medium-sized and smaller penguins, and they can all specialize in an overpopulated penguin environment,” Clarke said.

Despite the abundance of seafood and little competition, these penguins probably couldn’t get any bigger.

“I believe the kumimanu is close to the upper limit of a flightless seabird, and I don’t expect to find substantially larger penguins,” said Gerald Mayr, a paleontologist at the Senckenberg Research Institute in Frankfurt, Germany, who described the Kumimanu biceae, of 99 kg. Mayr, who was not involved in the new study, notes that heavier birds would likely crush their eggs.

As specimens of the first fossil penguins, kumimanu and petradyptes reveal that penguins gained weight rapidly after they stopped flying.

“Once you know you’re not flying anymore,” Ksepka said, “the sky’s the limit.”

_{Translated by Luiz Roberto M. Gonçalves}