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Science

New Zealand's First Land Mammal Discovered 154

Posted by kdawson from the furry-feet dept.
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."
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New Zealand's First Land Mammal Discovered More

New Zealand's First Land Mammal Discovered

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  • Or do genus biggus hairius footus not qualify as mammal.

  • well (Score:5, Interesting)

    by jrwr00 ( 1035020 ) <jrwr00@GIRAFFEgmail.com minus herbivore> on Wednesday December 13, 2006 @02:14PM (#17225734) Homepage
    I think maybe that fossil was carried over when the birds where hunting off the island

  • I disagree (Score:5, Interesting)

    by joe 155 ( 937621 ) on Wednesday December 13, 2006 @02:15PM (#17225746) Journal
    "has put paid to the theory that New Zealand's rich bird fauna had evolved there because they had no competition from land mammals"

    I don't really see how... one small mouse, even if there was 1 million of them, wouldn't really have made much difference to birds; it'd only be preditors that made a big difference

    • Re: (Score:3, Insightful)

      by Tmack ( 593755 )

      "has put paid to the theory that New Zealand's rich bird fauna had evolved there because they had no competition from land mammals"

      I don't really see how... one small mouse, even if there was 1 million of them, wouldn't really have made much difference to birds; it'd only be preditors that made a big difference

      They would make a difference... as food

      tm

    • Yeah, right, because mice never eat eggs (Score:5, Funny)

      by spun ( 1352 ) <loverevolutionary&yahoo,com> on Wednesday December 13, 2006 @02:25PM (#17225916) Journal
      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!

    • Re: (Score:2)

      by Lumpy ( 12016 )
      Yes and it would be IMPOSSIBLE for a bird to have eaten the mouse elsewhere and flown to that location and crapped or puked it out. It's not that far from mainland Oz to have eaten dinner in Oz and then head home with some mouse constipation.

      Owls crap out mice skeletons, safe to assume other birds do as well, until they find more than parts of one I'm still skeptical.

      • Re:I disagree (Score:4, Insightful)

        by CrimsonAvenger ( 580665 ) on Wednesday December 13, 2006 @02:38PM (#17226108)
        It's not that far from mainland Oz to have eaten dinner in Oz and then head home with some mouse constipation.

        Umm, New Zealand is about 1000 miles from Australia last time I checked.

        Hardly a short flight for anything but an albatross.

        • There is a remote chance that some sort of Albatross (during a famine or something?) could have picked up a mouse and flown back. There are a number of other seabirds, some of which (Shearwaters) are vicious enough to potentially go after mammals, but it still seems unlikely (as most seabirds hunt at sea and only return to land to nest).

          I think that scientists probably took into account everything we are saying now when they found the bird.

          The best thing I can come up with is that the fossil is that of a s

          • There is a remote chance that some sort of Albatross (during a famine or something?) could have picked up a mouse and flown back.

            Albatrosses eat fish, squid or crustaceans, depending on species of albatross. Mice aren't included.

            Even more significant, you're assuming that ONE (dead) mouse was brought to New Zealand 16 million years ago, and it just happened to get fossilized, and we just happened to find its skull. Yah, amazingly lucky things happen, but finding the ONLY mouse skull that has ever been o

          • Re: (Score:3, Informative)

            by Artifakt ( 700173 )
            Scientists tend to reject remote chances near automatically when it comes to fossils. Since only about 1 creature in 100 million or so ever gets found in fossil form (addmitedly a rough average), the odds of that also being a 1 in 100 million exception for other reasons become very much astronomical (or even just a one in a million chance does). If we have only 6 Foobarasaurus Smex fossils that are close enough to full skeletons to judge size well, and there were probably 600 million of them during the whol

    • Re: (Score:2, Insightful)

      by TheNicestGuy ( 1035854 )
      Another huge difference mammal competition can make to bird evolution is the fact that there have always been a lot of wily egg-eating mammals.
    • If anything, a thriving small rodent population could serve as a food source for the birds.  But, one tiny rodent does not hint at a larger population of mammals.  Gotta love slippery slope sensationalism.

    • Well, It Certainly Impacts the Theory (Score:5, Interesting)

      by eldavojohn ( 898314 ) * <eldavojohn@noSpAM.gmail.com> on Wednesday December 13, 2006 @02:29PM (#17225990) Journal
      I don't really see how... one small mouse, even if there was 1 million of them, wouldn't really have made much difference to birds; it'd only be preditors that made a big difference
      Well, I think the overall logic is that this ancient mouse and its affiliates would most likely have prospered in New Zealand and eventually evolved into something that fed on birds. In a lot of places, mammals have been more successful than birds. Now, there are a few like places Antarctica where birds are probably more successful than mammals but New Zealand and its surrounding islands (like the Dodo on Mauritius) were pretty special in this respect. So special, that (as I learned in Jared Diamond's "Guns, Germs & Steel") when humans arrived, many of the bird species had no fear of humans--only curiosity. They didn't have the thousands of years of living side by side with humans like elephants & zebras did in Africa to slowly train them to stay away at all costs. So its evident they never lived with predators but why were mice fossils found and not other mammals?

      So now we need to explain that the mouse and other mammals were either restricted by food sources or eliminated. It also has to explain why there aren't more mammals. What is it about New Zealand? Did a volcano periodically remove all life from the island so that only birds could repopulate it at some point? Perhaps the only mammals that survived a food shortage were mice which were subsequently overhunted by the birds? These are the new questions that now must be answered.

      So we're still left with this question of why these 1 million mice didn't evolve or why their bird eating relatives didn't thrive on the island. I heavily endorse and suggest Guns, Germs & Steel if you haven't had the time to read it. It asks questions about subjects like these that for a long time people just used the creation theories to explain. Now we're finally starting to look for answers as to why the way things are the way they are and why some populations of humans are better off or have more 'cargo' than others.

      • Re: (Score:3, Interesting)

        by jd ( 1658 )
        The birds in New Zealand are curious creatures. From the extinct Moa and Haast Eagle (both absolute giants) to the Kea, Kakapo and Kiwi, the birds in New Zealand have no characteristics that indicate ground-based predators. Your car is far more likely to be ripped to shreds by a psychotic flightless parrot than it is to be damaged in an accident with another vehicle. Fear? Those creatures show no fear! (In fact, their total reckless abandon probably drove the poor mouse out of its mind - I think it went ext

        • the birds in New Zealand have no characteristics that indicate ground-based predators.

          Don't worry, the ones that are still around in a few hundred years will.

          • Re: (Score:2)

            by jd ( 1658 )
            Doubt it. The ones left in a hundred years time will have beaks designed to rip steel doors off their hinges and have adapted their wings to be able to carry rugby balls.

      • Re: (Score:2)

        by mudshark ( 19714 )
        The megavolcano theory is certainly a possibility. Lake Taupo [minerals.co.nz] is a huge caldera that has erupted violently several times in very recent geologic history. All you'd need to do is look around the islands for evidence of a layer of rhyolitic ash deposits corresponding to an extinction horizon. Don't know if anything like this has been found, though....

      • Re: (Score:2, Insightful)

        by natedubbya ( 645990 )

        "So now we need to explain..."

        That's why I love reading evolution "research" papers. They explain and explain, and then something happens to show it doesn't work, so they come up with a completely different explanation, etc. etc. I mean, come on, how hand wavy can you get and still call it valid science?

        And no, I'm not anti-evolution (and no, not creationist, I'm just open to criticizing my own thoughts). I just enjoy how overly-serious people treat evolution theories, based on basically no evidence.

        • In science - we develop a theory, and then look for negating evidence.
          When we find it we revise the theory.

          Its the same from chemistry to astro-physics.

          • It's also worth noting that if we waited to use or rely on or extrapolate from the current theory, we would probably never get anywhere as a species. It is useful to rely on the best known theory. Simply because it is better than any other, it follows that it should produce the most beneficial effects, or at least the most predictable effects, when applied.

            Physics is especially susceptible to this; If people withheld judgement on Newton's theories, we would have missed out on a lot of things. If people h

    • Re:I disagree (Score:5, Insightful)

      by camperdave ( 969942 ) on Wednesday December 13, 2006 @02:32PM (#17226030) Journal
      Well, a few pigs killed off the dodo by eating its eggs. Millions of small rodents could put a significant dent in an ecosystem if they took a liking to bird eggs. And that's only a direct example. They could conceivably out-compete certain birds for seeds. They could be a perfect breeding ground for parasites. They could be lunch for the birds. Their rotting carcases could increase the fly populations, thus indirectly providing more food to the birds. There's dozens of ways that millions of mice could alter an ecosystem.
    • Well, what if the mammal preyed on the eggs of the birds and not the birds themselves? There could be significant effects on birth rates due to egg predation. This is evidenced by the population *increase* of wild turkeys in NY due to a *decline* of nest predators such as foxes, raccoons and skunks (die off from rabies) - in this case the corollary is also true.
    • Could this thing possibly had claws and been predatory on the birds themselves? Food for thought - probably not much else.

    • Re: (Score:2)

      by mrbooze ( 49713 )
      Rats and mice can *decimate* island ecosystems. They can climb well enough to get into nests and love the taste of eggs.

    • "has put paid to the theory that New Zealand's rich bird fauna had evolved there because they had no competition from land mammals"

      I don't really see how... one small mouse, even if there was 1 million of them, wouldn't really have made much difference to birds; it'd only be preditors that made a big difference
      Rats are a huge problem for native New Zealand birds now because they eat the birds' eggs.

    • Re: (Score:2, Insightful)

      by matt_morgan ( 220418 )

      Even very small mammals may eat the eggs of very large birds. In fact they often do.

      The real issue here is that every species fills a niche. A mammal filling a niche means there will be no bird filling that niche. Nonetheless, it's kind of a dumb comment (not yours--I mean the original one you're referring to); one mammal species 16 mya will have less impact on bird evolution than many mammal species existing throughout time. 16 my is a lot of time for evolutionary changes to take place.

  • Mammals?! Oh, my... (Score:4, Funny)

    by __aaclcg7560 ( 824291 ) on Wednesday December 13, 2006 @02:15PM (#17225750)
    I thought New Zealand only had hobbits and Peter Jackson.
    • You say that as though you don't think Peter Jackson is a hobbit.

  • Rich bird fauna (Score:1, Interesting)

    by Anonymous Coward
    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.

    Why? Seems easy to conclude that birds flourished and ate the rat things to extinction.

  • modify the theory (Score:5, Funny)

    by Johnny5000 ( 451029 ) on Wednesday December 13, 2006 @02:16PM (#17225766) Homepage Journal
    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.

    • Re: (Score:2)

      by spun ( 1352 )
      And over the course of 16 million years, during which time period most modern mammals evolved from mouse-like creatures, why did the ones in New Zealand not evolve into many various forms that would have competed with birds? I mean, if no mammals are there, it makes sense why no mammals would have evolved to compete with birds, but if even one is there for 16 million years, why did it not evolve into a plethora of new forms?

      • Re: (Score:3, Funny)

        by mr_mischief ( 456295 )
        One possibility is that this thing and all like it were already as dead as it is now. It's difficult for your offspring to evolve if you don't survive long enough to produce offspring.

      • Re: (Score:2)

        by cnettel ( 836611 )
        16 million years ago, our ancestors were still great apes, much larger than mice. Another well-kept secret for you: a majority of the mammalian species 16 million years ago evolved into extinction.
        • The average lifespan for a big cat species is only about 4 million years. For other large predators about 7 to 8 million, and for large grazing herbivores of various sorts, around 12 to 20 million (medium sized antelope-likes tend to last longer than cape buffalo-likes, as species go.). Small mammals, such as rodents and ungulates, do tend to last relatively unchanged, and 16 million years is actually pretty reasonable for a mouse-like species, with even 20 to 24 million being possible. I'm using species he

    • Re: (Score:2, Funny)

      by florist ( 657769 )
      So we go from "harmless" to "mostly harmless"?
    • So you might describe the land mammal as "mostly harmless"?

  • Corrected theory statement (Score:5, Insightful)

    by smbarbour ( 893880 ) on Wednesday December 13, 2006 @02:16PM (#17225772)
    Only a small change required to the theory:

    New Zealand's rich bird fauna had evolved there because they had little competition from land mammals.

    • Re: (Score:2)

      by HTH NE1 ( 675604 )
      I'd prefer this (DNA-inspired) phrasing:

      New Zealand's rich bird fauna had evolved there because they had no competition from land mammals, or at least none worth speaking of.

    • Re: (Score:2)

      by GeckoX ( 259575 )
      Perhaps evolved and thrived _because_ there were small mammalians available as a food source, but no large predators.

    • Only a small change required to the theory: New Zealand's rich bird fauna had evolved there because they had little competition from land mammals.

      Dammit, you just blew my whole thesis.

  • They don't have people living in NZ? Or is that why they call themselves Kiwis? (*Cough*).

  • One theory posits that ancient Australia... (Score:5, Funny)

    by Anonymous Coward on Wednesday December 13, 2006 @02:20PM (#17225832)
    ...established New Zealand as a colony for its most criminal mammals.

    I suspect these are the bones of a dirty, little rat.
    • ...established New Zealand as a colony for its most criminal mammals.

      Hah! You have it the wrong way round.

      Australia was colonised by people to whom it was said "Sod you, your going somewhere else!"

      New Zealand was colonised by people by whom it was said "Sod this, I'm going somewhere else!"

    • Re:One theory posits that ancient Australia... (Score:4, Funny)

      by vaughanf ( 748513 ) on Wednesday December 13, 2006 @04:57PM (#17228514)
      No, no, no, you have it all wrong, Australia was the penal colony.

      That's why we New Zealanders have so much respect for Australians.

      Their ancestors have stood before some of the most prestigious judges in England!

      On a related note, when going to Australia, there's a field on the form you fill in before entry asking if you have any criminal convictions. DON'T tell the customs people that you didn't realise it was still a requirement. They somehow fail to see the funny side.
  • Please people -let's try to stay on track, and not degenerate into evolution/religion flame wars. Slashdot is about nerd news - science, computers, etc. Evolution falls into that, and should be discussed here with the concept of that it is an accepted scientific process. If you wish to dispute that, please go to another website, where evolution is not accepted.

    Now on topic, those little mouse sized mammals really were the shock troops of mammalian invasion forces - they seemed to be pretty successful. I

    • Re: (Score:2)

      by jfengel ( 409917 )
      Part of science is being skeptical about everything, including (and especially) what seems completely obvious. Banning people who question evolution is just as dogmatic as a religious text.

      I'll concur that anybody promoting a purely religious six-day-creationism story really doesn't belong here. It's a theory that's been pretty vigorously refuted from a scientific standpoint, and there's no point in discussing it any further. Skepticism means questioning what you believe to be true, not pursing what's alrea

    • Please people -let's try to stay on track, and not degenerate into evolution/religion flame wars. Slashdot is about nerd news - science, computers, etc. Evolution falls into that, and should be discussed here with the concept of that it is an accepted scientific process. If you wish to dispute that, please go to another website, where evolution is not accepted.

      Am I missing something here? Who here was arguing evolution that it required this kind of comment? This might as well be an instigation for that sort

  • Food for the birds? (Score:4, Insightful)

    by jmagar.com ( 67146 ) on Wednesday December 13, 2006 @02:24PM (#17225894) Homepage
    judging by the size, then perhaps this mammal was not competition, but instead a source of food for the birds...

    I'd suggest a minor change to the theory instead of chucking the whole thing.

  • Theory (Score:1, Insightful)

    by sgt.greywar ( 1039430 )
    I particularly enjoy how *one* mammal fossil would somehow constitute "competetion" for all the birds there.

  • 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.

    The big question is what happened to the mammals? If mammals in New Zealand were wiped out millions of years ago, then the original "birds evolved without mammals" theory is quite valid. The only real way I see that happening is if New Zealand were completely covered by ice or some similar cata

    • Just a very few possibilities:

      1. Maybe NZ was inhabited by birds and mammals at one time, the lot of them got wiped out, and birds repopulated it from beyond water by island hopping but mammals didn't swim as far as the birds could fly. Maybe this one mouse fossil is from just before the catastrophe.

      2. Maybe it really was eaten elsewhere and was part of a dropping.

      3. Maybe only a few mammals that didn't make the evolutionary cut ever got onto NZ, and they died out before the big explosion in mammal evolutio
      • 5. Maybe the jaw is from some kind of early bat -- it's a mammal, yet it does what birds do, like flying and eating insects and fruits. I'm not sure a bat could make it to NZ from anywhere, nor that any bats evolved by that point. It's probably as feasiable an explanation as #4 until there's a reason to believe otherwise.

        New Zealand already has two native species of bat. They were the previously only known native mammals in NZ. This is why these articles are concentrating on the 'land mammal' angle.
        • That's a very interesting bit of information.

          I'm not a paleontologist, but it'd be interesting to know how they can be absolutely sure the differences between a land mammal and a flying mammal by the jaw alone. An argument that the jaw is better suited to a land mammal is not an argument that the creature couldn't have overcome a weakness of being a flying mammal with a jaw more suited to a land mammal.

          If a person saw a detached bill in the mud, their first thoughts would probably be of a duck, goose, or sw

          • Re: (Score:2)

            by khallow ( 566160 )

            I'm not a paleontologist, but it'd be interesting to know how they can be absolutely sure the differences between a land mammal and a flying mammal by the jaw alone.

            You can tell a lot from the jaw alone. Diet is the obvious one. But also, if the mammal were of the flying sort, the jaw would have evolved to be lightweight. And let's not forget that they got a hip too. That would indicate directly the stance of the animal.
          • I just saw on MSNBC that flying mammals may have been around 130 million years ago [msn.com].

            While the early specimen found is thought to have only been capable of gliding flight (think flying squirrels of today), that's about 80 million years before there's a fossil record of actual flapping bats, apparently. So maybe in New Zealand there's a partial fossil of a proto-bat that is an ancestor to the true bats. Maybe not.

            Unqualified assertions that a single curious fossil find prove anything are pretty silly. The idea
      • New Zealand already has native bats, they were the only known form of native mammal before now,

    • Re: (Score:2)

      by lcsjk ( 143581 )
      The land is covered by water after a rain of 40 days. The carcas of one rat floats around and finally ends up on the island of New Zealand after the flooding subsides where it freezes and becomes preserved for some 15 million years. Later the isolated island is inhabited by birds that have found it to be a safe place to live.

      It is highly unlikely that mammals lived on the island. However, finding the bones of that one floating rat after 15 million years----I think I'll go out and buy a lottery ticket!

      I

      • think it rained longer than 40 days, but at the time, man only had ten fingers on each hand and 10 toes on each foot.

        Death to the twenty-toed mutants!

    • Small mammals tend to be pretty hardy and numerous, but so do small birds. Catastrophism is still valid theoretically, and you're certainly allowed to suggest a disaster affected things without it being unscientific speculation (witness the current dinosaur extinction theories). But, birds gradually winning out over mammals locally is not really far fetched either. If you start with something like mice and sparrows, and the sparrow's descendants fill the predator and large grazer niches just a little faster
  • Seems more like the mice died off due to the large bird population killing them off.

    Forget competition they were just food.
  • That birthday prank we gave John by burrying down that old skeleton from ebay (at least now I know what animal it is) in his garden has gone way to far...
    • Dang that sucked - the link was supposed to be the movie poster for Ice Age with the sabre-toothed squirrel. Apparently, you can't link to the pic.

  • Full article available via PNAS as 'open access' (Score:5, Informative)

    by Buran ( 150348 ) on Wednesday December 13, 2006 @02:58PM (#17226412)
    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 [pnas.org]

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

    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).
    • PNAS considers this important enough that it has the article tagged as "open access" -- free for all to read.
      It's not what the PNAS editors think about it that made it Open Access. It's that the authors were enlightened enough to request that the article be Open Access, and willing to pay PNAS about $1000 to make it so. It is to the journal's credit that they offer authors the option, and that all articles are made Open Access after a few months.
  • God doesn't play easter egg hunts with fossils...
    He plays pin the quantum string on the white hole...

    FOSSIL!...FOSSIL!!- Lewis Black
  • but what's the point if we can't find out what it tastes like? Huh?

  • Bats (Score:2, Informative)

    by Mercedes308 ( 832423 )
    New Zealand has two species of native bats, would they count as mammals?

    • Re: (Score:2)

      by LWATCDR ( 28044 )
      If they are native I would say yes.
      Let's check.
      Warm blooded... yep.
      Gives birth to live young... yep.
      Produces milk from glands for it's young.. yep.
      Has hair... Yep...

      Classic mammal even by the good old 3rd grade definition that excludes the duck billed platypus and that other strange mammal that lays eggs.

    • Re:Bats (Score:4, Interesting)

      by Conanymous Award ( 597667 ) on Wednesday December 13, 2006 @05:58PM (#17229386)
      Bats do, of course, count as mammals, but we are speaking ground-dwelling mammals here. New Zealand supposedly never had those before the human invasion. No we know they had, once.

      Still, I don't see this that hard a fact to reconcile with the traditional view of NZ as a Kingdom of Birds. The animal was still only a small critter. Sure, critters as small as rats are known to have exterminated ground-dwelling bird species from isolated island ecosystems. But NZ is much bigger than Hawaii, Mauritius, Galápagos and other famous examples of island extinction. This would mean its bird-dominated ecosystems and bird species would have been much more robust and resistant to a mammalian threat. Why, there were large, flightless predatory birds on the island continent of South Africa before the Great American Interchange. And how about the ostrich, emu & co.? [wikipedia.org]

      This new fossil mammal also appears to represent a very ancient lineage dating back to early Cretaceous mammals. We know for fact these critters were not necessarily some übermammal bird-pwners: after the KT extinction (the one that killed the dinosaurs, y'know), for a short while birds were among the top predators, and there were many other flightless birds, too, all over the world. This seems to indicate that early mammals were not the bird menace modern placental mammals like rats, pigs, and cats (and us) are. Nothing mysterious going on here, methinks. You simply cannot compare an advanced Neogene placental to a primitive Cretaceous type of proto-shrew in terms of predatory efficiency.

      And how about this possibility: NZ only became a bird paradise after this critter and its relatives went the way of the dodo, for some reason or another?

  • Interesting. (Obligatory eyebrow raise.) (Score:5, Interesting)

    by M0b1u5 ( 569472 ) on Wednesday December 13, 2006 @03:25PM (#17226900) Homepage
    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.

    • Re: (Score:1, Informative)

      by Anonymous Coward

      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.

      The Pukeko's (Australian Purple Swamphen) being a poor flier is an urban legend. They're excell

    • Re: (Score:3, Informative)

      by mudshark ( 19714 )
      Pukeko are hell on mice, or anything that will fit in their beaks for that matter. They're quite effective hunters, as anyone who has free-roaming poultry in rural NZ will attest. So maybe that's where the little furry buggers went.

  • Not quite correct (Score:1, Informative)

    by Anonymous Coward
    The country has long been thought to have been devoid of land mammals until recent times.
    There were and still are in New Zealand a few species of bat that walk around on the ground (I'm not making this up), who flew over from Australia without human introduction.
  • Creationists could use this argument to refute that mice evolved from reptiles... if they accepted fossil dating explanations.

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