A newly-described ancient marine dolphin fossil from the Waitaki region is of the same super family as the endangered Ganges river dolphin, according to University of Otago, New Zealand, research.
Professor Ewan Fordyce and his PhD student Yoshi Tanaka have formally described and named the new fossil species Otekaikea huata, which refers to the marine limestone formation it was deposited in and the Maori word for spear.
Otekaikea huata joins only a few other dolphins known from about 22.5 to 24.5 million years ago.
The fossil was discovered in the Hakataramea River valley. At that time, New Zealand was a cluster of small low islands with extensive shallow warm seas.
Professor Fordyce says that in life, the fossil dolphin's skull was about 80cm long and its body around 2.6 metres.
''The fossil has a surprisingly long projecting tusk that became broken in life, but whether this was from fighting or feeding is uncertain. It's likely that it had four or more tusks in life, but these others weren't preserved,'' Professor Fordyce says.
He says Otekaikea huata belongs in the once-diverse and widespread dolphin group called Platanistoidea. This group is now extinct in the oceans, and is represented only by the endangered Ganges river dolphin and Indus river dolphin subspecies.
''Our study is one of several showing that the South Asian river dolphin lineage was more diverse in the past. It is not clear why this lineage became extinct in the oceans, but it could have been due to long-term climate change and competition from later-evolving ocean dolphins,'' he says.
The findings are published in the May-August issue of the journal Palaeontologia Electronica.