New research has revealed that it wasn’t just New Zealand that once played home to giant marine birds, with fossil evidence revealing a similar animal once roamed the oceans around in Japan, the USA, and Canada. The research, published in the Journal of Zoological Systematics and Evolutionary Research, found that the bones of New Zealand’s mega penguins which lived 62 million years ago shared striking similarities with those from a much younger group of birds, the plotopterids, found in the Northern Hemisphere. The findings indicate that plotopterids looked very much like their giant Kiwi counterparts, and it’s hoped their discovery will further our understanding of how birds came to use their wings to swim instead of fly.
The first evidence of penguins was found in Waipara, North Canterbury, in New Zealand where nine distinct species have now been identified. They ranged in height from small birds to some around 1.6 meters (5.2 feet) tall, which as a 1.65 meter-person I find quite intimidating.
Plotopterids didn’t appear in the evolutionary record until 37 to 34 million years ago, with fossils discovered at sites in North America and Japan. Though more modern birds, the plotopterids went extinct around 10 million years later, but their fossil evidence indicates they too used their wings to zoom through the ocean rather than the air.
To establish this, the study researchers decided to compare the fossilized remains of plotopterids against those of the giant penguin species Waimanu, Muriwaimanu, and Sequiwaimanu that roamed New Zealand 60 million years ago, from the Canterbury Museum’s collection. Their analyses revealed that the birds shared several characteristics including a long beak with slit-like nostrils, chest and shoulder bone morphology, and wing structure. The findings suggest that both groups of birds evolved to be strong swimmers, hunting in the deep sea to catch a marine meal.
There were also similarities in the heights of the birds, with the largest known plotopterids measuring over 2 meters (6.6 feet) long, compared to New Zealand’s giant penguins with a maximum height of 1.7 meters (5.5 feet). Plotopterids, however, do differ significantly from their Southern Hemisphere counterparts in that they’re more closely related to boobies, gannets, and cormorants rather than penguins.
“These birds evolved in different hemispheres, millions of years apart, but from a distance you would be hard-pressed to tell them apart,” said Dr Paul Schofield, curator for Canterbury Museum, in a statement. “Plotopterids looked like penguins, they swam like penguins, they probably ate like penguins – but they weren’t penguins.”
It’s possible this example of convergent evolution – similar traits evolving in unrelated species – could hold the key to explaining why birds across the globe adapted to life in marine environments rather than aerial ones.
“Wing-propelled diving is quite rare among birds; most swimming birds use their feet,” said Dr Gerald Mayr of the Senckenberg Research Institute and Natural History Museum, Frankfurt. “We think both penguins and plotopterids had flying ancestors that would plunge from the air into the water in search of food. Over time these ancestor species got better at swimming and worse at flying.”