An international study, led by former University of Otago PhD candidate Dr Tatsuro Ando, named the new species of fossil penguin Pakudyptes hakataramea and described it as being very small — about the same size as the little blue penguin — with anatomical adaptations that allowed it to dive.
Dr Ando and researchers from Otago, Ashoro Museum of Paleontology, Okayama University of Science and Osaka University analysed three bones from the fossil — a humerus, a femur and an ulna, which were found by late University of Otago palaeontologist Emeritus Prof Ewan Fordyce.
Dr Ando said Pakudyptes played a huge role in the evolutionary history of the bird.
"In particular, the shape of the wing bones differed greatly, and the process by which penguin wings came to have their present form and function remained unclear."
The humerus and ulna highlight how penguins’ wings have evolved, he said.
"Surprisingly, while the shoulder joints of the wing of Pakudyptes were very close to the condition of the present-day penguin, the elbow joints were very similar to those of older types of fossil penguins.
"Pakudyptes is the first fossil penguin ever found with this combination, and it is the key fossil to unlocking the evolution of penguin wings."
Co-author and University of Otago dentistry researcher Dr Carolina Loch said analysis of the internal bone structure conducted at the Sir John Walsh Research Institute, was compared with data on living penguins provided from the Okayama University of Science, which showed these penguins had microanatomical features suggestive of diving.
Modern penguins have excellent swimming abilities, largely due to their dense, thick bones that contribute to buoyancy during diving.
In Pakudyptes, the bone cortex was reasonably thick although the medullary cavity, which contains bone marrow, was open, similar to what we see in the modern little blue penguin, which tends to swim in shallow waters.
The ability for Pakudyptes to dive and swim comes down to the distinctive combination of its bones.
Bones such as the humerus and ulna show areas for attachment of muscles and ligaments which reveal how the wings were being used to swim and manoeuvre under water.
Dr Loch said fossil penguins were usually large — about 1m in height.
"Penguins evolved rapidly from the late Oligocene to early Miocene, and Pakudyptes is an important fossil from this period.
"Its small size and unique combination of bones may have contributed to the ecological diversity of modern penguins."
