The biggest penguin that ever existed was a “monster bird”

New Zealand has been a haven for land birds for ages. The absence of terrestrial predators allowed flightless parrots, kiwis and moas to thrive. Now researchers are adding two prehistoric penguins to this floor aviary. One species is a burly behemoth that waddled along the New Zealand coast nearly 60 million years ago. At nearly 350 pounds, it weighed as much as an adult gorilla and is the heaviest penguin known to science.

Alan Tennyson, a paleontologist at Museum New Zealand Te Papa Tongarewa, discovered the giant seabird’s bones in 2017. They were deposited on a beach known for its large cannonball-like concretions called Moeraki Boulders. Tidal churning has cracked open many of these 57 million year old rocks, revealing pieces of fossilized bone within.

Dr. Tennyson and his colleagues have identified the fossilized remains of two great auks. The humerus of one, measuring more than nine and a half inches long, was nearly twice as large as those found in emperor penguins, the largest living penguin. Other rocks provided bones of a smaller, more complete penguin species that also appeared larger than a modern emperor penguin.

Researchers described the ancient birds Wednesday in the Journal of Paleontology. They named the larger penguin Kumimanu (a mixture of the Maori words for “monster” and “bird”) fordycei and named the smaller penguin Petradyptes (“rock diver”) stonehousei.

By creating 3D models of Kumimanu’s huge humerus and comparing its size and shape with the fin bones of prehistoric and modern penguins, researchers estimate the ‘monster bird’ weighed 340 pounds – 15 pounds heavier than Lane Johnson, right tackle anchor for the Philadelphia Eagles offensive line 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 the Kumimanu makes it difficult to determine its height. Dr. Ksepka estimates he was about 5ft 2in tall, giving him a stocky build. Nor was Petradyptes a lightweight. It weighed 110 pounds, making it heavier than modern emperor penguins, which top out at 88 pounds.

Kumimanu and Petradyptes roamed the waters off New Zealand at a key time in ocean history, according to Dr 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. This meant that there were few things that would bother a penguin the size of a black bear.

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

Despite their prodigious size, Kumimanu and Petradyptes possessed primitive flippers reminiscent of modern seabirds like penguins and flying and diving puffins. Julia Clarke, a paleontologist at the University of Texas at Austin who studies the evolution of diving in birds and was not involved in the new study, said it would make sense for early penguins like Kumimanu and Petradyptes to retain several characteristics left by their ancestors. ‘ airborne lifestyle.

The new species adds evidence that prehistoric penguins grew huge before honing their fins into paddle-like appendages. Heavier seabirds are able to dive deeper and longer than their lighter counterparts, Dr Ksepka said. The extra belly would have also helped these penguins stay warm in the water.

While Kumimanu was powerful, he did not crowd out his lesser penguin cousins. “You have very large penguins that eat the biggest prey and you also have medium-sized and smaller penguins, and they can all specialize in a crowded penguin environment,” Dr Clarke said.

Despite plenty of seafood and little competition, these penguins probably couldn’t grow.

“I believe Kumimanu is close to the upper limit of a flightless seabird and I don’t expect to find much larger penguins,” said Gerald Mayr, a paleontologist at the Senckenberg Research Institute of Frankfurt, who described the closely related 220-pound Kumimanu. biceps. Dr. Mayr, who was not involved in the new study, notes that heavier birds would most likely crush their eggs into yellow crumbs.

As some of the earliest fossil penguins, Kumimanu and Petradyptes reveal how quickly penguins gained weight after ceasing to take flight.

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