Penguins probably evolved about 50 million years ago, and New Zealand has yielded clues to their origins.
The Kakanui fossil
During a visit to the North Otago coastline, Walter Mantell (whose father Gideon discovered the first dinosaur fossil) acquired a strange bone unearthed from the limestone deposits around Kakanui.
In Britain it came to the attention of Thomas Huxley, the paleontologist as well known for his support of Charles Darwin as for his expertise with old bones. In 1859, the year Darwin published On the origin of species, Huxley published a scientific paper describing Mantell’s somewhat damaged bone as the tarsometatarsal (fused ankle bone) of an extinct penguin, which he named Palaeeudyptes antarcticus (‘ancient winged diver of the south’).
This was a wonderful piece of scientific deduction. Fortuitously for Huxley, the tarsometatarsal is the most distinctive bone that penguins possess, and it is dense – unlike the hollow bones of flying birds. Non-pneumatic bones (without air spaces) are characteristic of penguins and aid their diving by counteracting the buoyancy of water. Unfortunately no other specimens of Palaeeudyptes antarcticus have ever been found. All that is known of the world’s first-discovered fossil penguin species is what can be gleaned from a broken ankle bone in a drawer in London’s Natural History Museum.
From the age of the limestone deposits around Kakanui, it is likely that Palaeeudyptes lived somewhere between 23 and 34 million years ago: not so old by penguin standards, and certainly not by those of birds.
The Waipara fossil
Birds have existed for about 150 million years. Penguins evolved from flying ancestors, and perhaps the best evidence for that comes from Waipara, about 50 kilometres north of Christchurch. Waipara is known for its vineyards, but its sun-baked soils have also yielded treasure from a vintage 55 million years ago: the fossilised bones of a precursor penguin.
From a few brown fragments of shoulder and flipper bones it was possible to deduce that they belonged to a diving bird: the main bone in the flipper is non-pneumatic, and flattened for paddling like those of modern penguins. However, features of flying birds are still writ within its anatomy. The bones are more fragile than a typical penguin’s, and some are shaped like those of some flying birds.
The Waipara specimen – named Waipara penguin (Waimanu tuatahi) – may be a snapshot of an evolutionary event as significant to penguins as the moment when our ancestors began to walk upright: the point at which their ancestors abandoned flight in favour of life in the sea.