Ancient marine fossil found
A unique fossil found at the tip of the South Island has been recognised as a 20-million-year-old marine ancestor.
The fossil, discovered near Cape Farewell, was collected and analysed by geologists at the University of Otago.
They described it as a close relation to the ancestors of modern dolphins and toothed whales.
Professor Ewan Fordyce and his PhD student, Dr Gabriel Aguirre, dubbed the fossil Papahu taitapu, and said it was the first of its kind ever found. This made it a significant addition to the fossil record of dolphins from the southern hemisphere.
Papahu is estimated to have lived between 19 million and 20 million years ago, making it one of the few dolphins dating to the start of the Miocene epoch.
"New Zealand was substantially under water back then," Fordyce said.
"There were wide shallow seaways. We know also that the climate was fairly warm, a lot warmer than today, with water temperatures down south about 18 degrees [Celsius] or warmer – good for swimming!"
Judging from the size of Papahu's skull, the dolphin was about 2 metres long – roughly the size of a common dolphin – and likely had "many simple conical teeth", he said.
Features of the skull showed that it was distinct from all previously reported fossils, which was why the dolphin could be formally named as a new form.
"When we compared Papahu with both modern and fossil dolphins we found that it belongs in a diverse and structurally variable group of ancient dolphins that evolved and spread worldwide 19 million to 35 million years ago," Fordyce said.
"All of those ancient dolphins including Papahu and others, such as shark-toothed dolphins, are now extinct.
"They have been replaced by the modern dolphins and toothed whales, which diversified within the last 19 million years."
It was not clear why Papahu and other ancient dolphins went extinct.