Recent discoveries across Japan, USA and Canada have uncovered the fossilized remains of massive ancient birds, very similar to the giant penguins that used to live in New Zealand. Research into these specimens has now also revealed why these massive seabirds began to swim instead of fly.
There are perhaps no group of animals that are more associated with Antarctica and the seas of the southern hemisphere than the penguins. These flightless birds are synonymous with the region and have lived there for over 62 million years. Whilst those we see today have remained largely unchanged in that time, some of their less-lucky relatives were much different, such as the giant penguins of New Zealand. These ancient seabirds could grow as tall as a man and were thought to be the only giants of their kind. However recent discoveries in Japan, USA and Canada have shown that the northern hemisphere once had their own giant penguin-like creatures, known as plotopterids. A new study into the similarities and differences between the giant penguins and their northern doppelganagers, has also revealed why these seabirds gave up flying and started diving instead.
The giant penguins
Around 62 million years ago the first penguins began swimming in the warm tropical seas surrounding what is now known as New Zealand. Palaeontologists there have found the fossilised bones of multiple species ranging in size from smaller birds, similar in size to today’s yellow-eyed penguin, all the way up to 1.6 metre giants. The tallest of which include species such as copepteryx, kumimanu, waimanu, muriwaimanu and sequiwaimanu. Examples of these enormous seabirds can be found displayed at the Canterbury Museum in New Zealand, where research comparing them to the newly discovered plotopterids took place.
Whereas the giant penguins of the south all lived in the region surrounding ancient New Zealand, the discovery of plotopterids has now occurred across the northern hemisphere in Japan, Canada and across the United States. By comparing the remains of these northern doppleganagers to their southern relatives, researchers from Canterbury Museum, the University of Washington and the Senckenberg Research Institute in Frankfurt, have now revealed new information about both groups and how similar they really are. The recently published their findings in a new study released in the Journal of Zoological Systematics and Evolutionary Research.
Similarities & differences
The main similarity between plotopterids and the giant penguins is size. Both groups were extraordinarily large for seabirds, with the plotopterids reaching an even more impressive 2 metres tall. In addition to this they shared long beaks with slit-like nostrils, similar chest and shoulder bones, and wingspans. All of which suggests that both groups used their wings to propel them deep underwater in search of food. “What’s remarkable about all this is that plotopterids and ancient penguins evolved these shared features independently” says Dr Vanesa De Pietri, a curator at the Cantebury Museum involved in the study, talking in a press release.
Although the two groups do share some striking similarities in size and lifestyle, there are also some big differences that tell them apart. Firstly they appeared at different points in history. Whereas the giant penguins emerged in New Zealand around 62 million years ago, the plotopterids emerged around 37 million years ago at the same time their southern relatives disappeared. Although the northern giants did share a lot of physical features with the penguins, they were still more closely related to modern northern hemisphere seabirds, such as boobies, gannets and cormorants. Dr Paul Schofield, another curator at the museum, explains that “these birds evolved in different hemispheres, millions of years apart, but from a distance you would be hard pressed to tell them apart.”
These similarities between the two groups despite their differences is what is known as convergent evolution, where both groups independently evolved similar traits without a recent common ancestor. Dr Gerald Mayr, from the Senckenberg Research Institute in Frankfurt, says the parallels in the evolution of the bird groups hint at an explanation for why birds developed the ability to swim with their wings. He explains that “wing-propelled diving is quite rare among birds; most swimming birds use their feet. 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.”