New Zealand's First Land Mammal Discovered

Bob Beale writes to clue us to big news from New Zealand. The country has long been thought to have been devoid of land mammals until recent times. No mammal fossils had ever been found there; but now one has. From the article: "Small but remarkable fossils found in New Zealand will prompt a major rewrite of prehistory textbooks, showing for the first time that the so-called 'land of birds' was once home to mammals as well. The tiny fossilized bones — part of a jaw and hip — belonged to a unique, mouse-sized land animal unlike any other mammal known... The fact that even one land mammal had lived there, at least 16 million years ago, has put paid to the theory that New Zealand's rich bird fauna had evolved there because they had no competition from land mammals."

Comments

well

[jrwr00]

I think maybe that fossil was carried over when the birds where hunting off the island

modify the theory

[Johnny5000]

The fact that even one land mammal had lived there, at least 16 million years ago, has put paid to the theory that New Zealand's rich bird fauna had evolved there because they had no competition from land mammals."

OK, that theory is total crap now.
Here's the new theory:

New Zealand's rich bird fauna had evolved there because they had only a little bit of competition from one tiny land mammal.

One theory posits that ancient Australia...

[Anonymous Coward]

...established New Zealand as a colony for its most criminal mammals.

I suspect these are the bones of a dirty, little rat.

Re: Birds hunting off-shore

[TheNicestGuy]

Not likely. The article is placing this fossil around 16 mya (million years ago), while New Zealand was as isolated from all other landmasses as it is today by 60 mya at the latest. Unless that hunting bird had a range as wide as the Tasman Sea (about 2,000 km), it couldn't have gone off-shore to get mammals.

Yeah, right, because mice never eat eggs

[spun]

Mice also never eat any kind of insects or seeds that birds eat. In fact, mice and birds have never and will never compete for resources. Long live the mighty mouse/bird alliance!

Full article available via PNAS as 'open access'

[Buran]

I work at a major medical school in the U.S., and so the first thing I did when I read the linked article (I know, I know, GASP!) was find out what journal this was published in -- we have online subscriptions to hundreds of journals, so surely I could go to the primary source. PNAS considers this important enough that it has the article tagged as "open access" -- free for all to read.

Miocene mammal reveals a Mesozoic ghost lineage on insular New Zealand, southwest Pacific -- Worthy et al., 10.1073/pnas.0605684103 -- Proceedings of the National Academy of Sciences

The abstract is standard HTML, but the full article is in PDF format (link to the full article PDF).

Citation:

Worthy, T. H., A. J. Tennyson, M. Archer, A. M. Musser, S. J. Hand, C. Jones, B. J. Douglas, J. A. McNamara and R. M. Beck (2006). Miocene mammal reveals a Mesozoic ghost lineage on insular New Zealand, southwest Pacific. Proc Natl Acad Sci U S A.

(no volume or page numbers as this article has not yet been published in print).

Interesting. (Obligatory eyebrow raise.)

[M0b1u5]

Interesting.

The fact we have native mammals (bats) in NZ hasn't really been discussed yet. How does that fit in with the observation of a mouse-sized land mammal 16 million years ago?

I find it annoyingly hard to reconcile, as we know that "Life will find a way" - and historically, land mammals have been particularly agressive in their expansion into new habitats, even going back to the sea (Ambulocetus) and taking on the birds (Bats et al).

Someone suggested volcanic activity - but this only applies to the North Island and the top of the South Island. The Taupo "eruption" og 86AD was reported by the chinese and the romans at the time. More than 30 cubic kilometres of matter was ejected in as little as 7 minutes.

However, this is dwarfed by the explosion 20,000 years ago, where over 2,000 cubic kilometres were ejected, as the magma chamber below Lake Taupo collapsed. The ferocity of this event is simply too large to imagine, and the landscape of the North Island was almost totally covered in ignumbrite, a gassy, fast flowing lava, expanding our from the crater at close to the speed of sound, in a wall some 200-300 metres tall...

The resulting Rhyolite domes from previosu explosions were actually topped by the outflow.

However, even as close as 5 kilomtres from the vent, some plant and animal life survived, and as the trillions of litres of water held loosely by the ignumbrite ran swiftly back to the lake area, and the remains of the North Island forests burned in one of the greatest fires in pre-history, and the rock cracked and cooled under muddy rain, the animals, birds, and plants made their way back into the landscape.

So - no - Taupo couldn't wipe out the land mammals of New Zealand, and the South of the South Island is almost entirely devoid of volcanos: Dunedin and Lyttleton volcanos were small, and not very violent in terms of the entire island.

There is an alternative available. The "Pukeko" is a common bird in New Zealand, and they are very poor flyers - certainly not capable of flying from Australia, where they evolved (They are the Australian "Swamp Hen") and yet they florish in New Zealand. They have only been here for a few thousand years. The best theory is that they came across on flotsam ejected from rivers during large storm events in Australia.

If Pukeko cxan arrive that way, then small mammals might also survive to arrive in New Zealand, but the number who arrived might not have been sufficient to maintain a good breeding pool, so the species might go extinct due to the lack of genetic diversity.

This would explain the discovery, the lack of other land mammals and the lack of fossils: if there were bugger all who ever floated over, then we are spectacularly lucky to even have found these ones.

That's my story anyway.