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Otago researchers reveal new NZ fossil dolphin

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Wednesday, 22 January 2014 10:01am

A newly recognised fossil dolphin from New Zealand, dubbed Papahu taitapu, is the first of its kind ever found and may be a close relation to the ancestors of modern dolphins and toothed whales, according to University of Otago researchers.

Professor-Ewan-Fordyce-and-DolphinProfessor Ewan Fordyce examines the Papahu skull. Credit RE Fordyce.

Papahu lived 19–22 million years ago, and is one of the few dolphins to be reported globally dating to the start of the Miocene epoch. Judging from the size of its skull, Papahu was about two metres long, roughly the size of a common dolphin.

Dr Gabriel Aguirre and Professor Ewan Fordyce, from the University’s Department of Geology describe and interpret Papahu in the latest issue of Journal of Vertebrate Paleontology. This work was part of Dr Aguirre’s PhD research.

Dr Aguirre says that like most living dolphins, Papahu had many simple conical teeth, but its head was probably a bit wider, and not as high-domed. It lived at a time of global warmth, in shallow seas around Zealandia – or proto-New Zealand – along with ancient penguins and baleen whales.

The skull, one jaw, and a few other parts of Papahu taitapu were found in marine sedimentary rocks in the Cape Farewell region of northern South Island. The researchers used the Māori name ‘taitapu’ to honour this region, and ‘Papahu’ is a Māori name for dolphin. Only a single specimen has been found so far and the fossil is housed in the University’s Geology Museum.

“Our study of structures of the skull and earbone suggest that Papahu could make and use high frequency sound to navigate and detect prey in murky water. They probably also used sound to communicate with each other,” says Dr Aguirre.

Features of the Papahu skull can be used to analyse relationships with other dolphins and toothed whales. That work shows that the skull is distinct from all previously-reported fossils, which is why the dolphin can be formally named as a new form, he says.

“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 world-wide 19–35 million years ago. All of those ancient dolphins including Papahu and others, such as shark-toothed dolphins, are now extinct,” says Professor Fordyce.

“They have been replaced by the ‘modern’ dolphins and toothed whales, which diversified within the last 19 million years,” he says.

It is not clear, however, exactly why Papahu and other ancient dolphins went extinct, he added.

For more information, contact:

Professor Ewan Fordyce
Department of Geology
University of Otago
Tel 64 3 479 7510
Email: ewan.fordyce@otago.ac.nz

Background information:

What is it?

A fossil dolphin that represents the first of its kind ever described.

Why is it important/ significant?

It belongs to a time range that is poorly represented by fossil dolphins and whales. It is a significant addition to the fossil record of fossil dolphins from the Southern Hemisphere.

Where is it from?

From New Zealand: the northern tip of South Island, near Cape Farewell.

When did it live?

The only known specimen lived in Early Miocene times, 22–19 million years before present. Probably the dolphin lived for 10–20 years, similar to small modern-day dolphins, but it’s not possible to resolve the exact geological age more accurately. If other specimens are found in association with the right sort of age-diagnostic fossils, it should be possible to pin down the age better.

How was it collected, prepared and studied?

The specimen was collected using a portable rock drill and geology hammers. The dolphin skull was excavated using small pneumatic chisels and dilute acid, in the fossil laboratory of the Department of Geology, University of Otago.

Formal reference and abstract

Aguirre-Fernández, G., and R. E. Fordyce. 2014. Papahu taitapu, gen. et sp. nov., an early Miocene stem odontocete (Cetacea) from New Zealand. Journal of vertebrate paleontology 34:195-210. Abstract: The early Miocene is one of the least understood intervals in cetacean evolution. A new early Miocene dolphin described here, Papahu taitapu, gen. et sp. nov. (family incertae sedis, Cetacea, Odontoceti), is from the Kaipuke Formation (21.7-?18.7 Ma) of North West Nelson, New Zealand. The holotype of Papahu taitapu includes a skull with an open mesorostral canal, a broad-based rostrum (broken anteriorly), two pairs of premaxillary foramina, a slight bilateral asymmetry at the antorbital notches, a slight intertemporal constriction exposing the temporal fossa and the lateral wall of the braincase in dorsal view, and single-rooted (and probably homodont) teeth. The periotic has an inflated, spherical pars cochlearis and an anterior process with the anterointernal sulcus and a recurved lateral sulcus well developed. The skull size indicates a body length of about 2 m. Papahu taitapu plots cladistically in a cluster of archaic dolphins variously referred to as Platanistoidea or as stem Odontoceti. It matches no family described so far, but cladistic relationships for comparable odontocetes are not yet resolved enough to justify family placement.

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