A new fossil discovery has shown that New Zealand’s old monster penguins were not the only human-sized, flightless birds that waddled around our planet tens of millions of years ago.
Recent discoveries in North America and Japan indicate that giant penguin-like creatures were trotting in the northern hemisphere as well. And these birds could have been bigger.
The strange thing is that the now extinct group of birds, known as Plotopterids, are not at all related to penguins – but they look remarkably similar and probably used their fin-like wings in a similar way.
The earliest penguin ancestors first appeared in what is now New Zealand a little over 60 million years ago. Plotopterids developed in the northern hemisphere much later than their southern counterparts, only appeared 37 to 34 million years ago and disappeared a total of 1
“These birds have evolved in different hemispheres millions of years apart, but it is difficult to distinguish them from a distance,” says zoologist Paul Scofield, curator at the Canterbury Museum.
“Plotopterids looked like penguins, they swam like penguins, they probably ate like penguins – but they weren’t penguins.”
In a fascinating twist, this group of old flightless birds is more closely related to modern birds that fly well – gannets, gannets and cormorants. We have understood a lot more about Plotopterids in recent years, but this is the first time that their anatomy has been compared in detail to ancient penguins.
The researchers analyzed the fossilized remains of 16 individual plopterids alongside five representatives of three ancient species of penguins and found many remarkable similarities and some significant differences.
Both plotopterids and old penguins had long beaks with slit-like nostrils, comparable breast and shoulder bones and similar wings. While some old penguins rose 1.8 meters high, the largest plotterids were over 2 meters high.
It is hard to imagine a bird larger than a human being diving through the water, but it seems that this was once a reality in both the northern and southern hemisphere.
Over: Artist’s impression of Kumimanu biceae, an extinct giant penguin, next to a human diver.
Although plotopterids have large webs like penguins, the authors believe that they are likely to swim underwater and, based on their anatomy, rely mainly on their wings as fins.
“Diving with wing drive is quite rare in birds. Most swimming birds use their feet,” says ornithologist Gerald Mayr from the Senckenberg Research Institute and Natural History Museum in Frankfurt.
“We believe that both penguins and plotterids had flying ancestors who plunged into the water in search of food. Over time, these ancestors were able to swim better and fly less.”
The fact that this happened in distant related organisms millions of years apart and on opposite sides of the world is really remarkable. It is what scientists call “convergent evolution”, in which similar features develop in different species under similar environmental conditions.
In this case, two separate groups of flightless birds developed the anatomy they would need to search for food deeper and deeper underwater. It turned out to be remarkably similar.
“We therefore assume that plotters and penguins had ancestors who carried out air raids to dive into the water and reduce the energy costs of reaching greater depths,” the authors write.
We need to dig more to find out why one line of these remarkable birds has survived while the other has been forgotten.
The study was published in the Journal of Zoological Systematics and Evolution Research.