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NEW ZEALAND'S WONDERFUL LITTLE WORLD
Hi everyone. I believe Nick Longrich started off another thread on the fauna of
New Zealand, asking where all the mammals were and all that. Ronald Orenstein
beat me to it by providing information, but here are a few extra bits and
pieces.. I'll bring it round to dinosaurs I swear...
NEW ZEALAND'S MAMMALS
> >Now, what the HELL happened to all the mammals?
> To the best of my knowledge there is no evidence whatever that terrestrial
> mammals ever inhabited New Zealand (if you exclude the cryptozoological
> rumours of the so-called "waitoreke").
(Also, North Island has a hairy hominid cryptid! I'm steering into no-go
territory here, but note that the waitoreke has been seriously discussed by a
number of mammalogists. L.H. Matthews, in his definitive tome on otters
(_Otters: A Study of the Recent Lutrinae_), wondered if it was a feral otter
introduced by Indians (!). The suggestion (I will not attribute it here) that
waitoreke is a descendant of amphibious synapsids like _Procynosuchus_ is
Anyhow, yes, New Zealand lacks a record of terrestrial mammals. It's also devoid
of non-mammalian synapsid fossils. Only whales, bats (2 or 3 sp., see below) and
recent Maori and European introductions are there. But were there _ever_ mammals
in NZ? No real reason why not. Terrestrial mammals may have gotten to NZ in the
Cretaceous (before rifting from Australia approx. 80 mya), but got killed off
by later extinctions. NZ has a pathetic record of terrestrial fauna, and nobody
really knows why. It may be due to NZ's highly acidic soils, but perhaps there's
no one really looking hard enough (not my suggestion NZ!). Joseph McKee is
attempting to remedy part of this situation, and has informed me that 'the hunt
for NZ's mammals is on'. He thinks they may be there.
But perhaps they're not. Speculations explaining their absence include that of
Stevens (1989), who wondered if 'climatic limitations or lack of suitable land
connections' during the Lower Cretaceous prevented mammal invasion (monotremes
were in Australia at this time). Speculations aside, we just don't know.
What would these mammals be, if they were there? Relying on the fossil record,
the only candidates (so far as I know) are monotremes. By the Lower Cret,
Australia had _Steropodon galmani_, and though S. America and presumably
Antarctica had moderately diverse marsupial, dryolestid, triconodont etc.
assemblages (Molnar 1989), as far as is presently known none of these got as far
as Australia (and, therefore, never as far as NZ). _Tingamarra_, a basal
ungulate from the Eocene, is Australian. Just what it shows is very open to
interpretation and I shan't bother to speculate.
> Certainly even if there were
> mammals on New Zealand at the time of its breakaway they could not have
> lasted long, because the radiation of birds in New Zealand seems highly
> likely to represent evolution in the absence of mammalian competitors.
This is correct. If NZ had native mammals, they would have to be small,
relatively inconspicuous forms, and if this is so, the diversity of NZ birds
does not dictate their absence. Also, presumably - if these mammals _were_ there
- they went extinct before the major radiation that produced Recent NZ birds,
and thus the vulnerability of many of NZ's birds to predation is also a straw
man. However, the cryptic habits and appearance of some NZ taxa strongly suggest
that they were predated upon naturally. Two extinct raptors (_Harpagornis
moorei_, biggest known accipitrid ever at up to 13 kg, and an ?unnamed goshawk-
like form, up to 3-4 kg) were evidently part of this selective pressure on the
avifauna, and it is remotely possible that mammals may have been too.
> Remember that 80 mya is still middle-to-late Cretaceous, and many of the
> mammalian lineages around at that time are no longer with us anywhere. I
> do not know (someone here must) what Cretaceous mammal lineages are known
> from Gondwana, that might possibly have been on New Zealand at the time of
> its breakaway. But I would have expected a fairly small fauna of little
> jobs on NZ at best, and these may well have disappeared through natural
> attrition at almost any time.
In reality, Cainozoic NZ was far from the pressure-free island paradise that
many books say it was. We know it was affected as adversely as elsewhere by the
K-T event, as its diverse dinosaurs and marine reptiles disappear at the end of
the Maastrichtian. In the Oligocene, NZ underwent a profound uplift phase. The
NZ Alps created by this phase may have initiated the speciation of moa that
produced Recent taxa. The production of all this new elevated land presumably
reduced forest habitat previously extensive over NZ, and may have caused
extinctions. Similarly, but far more catastrophic, was the 'Great Drowning' when
the affects of isostatic equilibrium (following the Oligocene orogeny) meant
that most of NZ became submerged. With only about 18% of the present-day land
area exposed, selective pressures on the biota must have been immense. If any
lineage was in trouble prior to this event, this was perhaps 'the last straw'.
> Too bad, too - it would be fun to turn up a
> zalambadestid or a multituberculate still alive there. Maybe the waitoreke
> is worth hunting for after all....
Now there's a thought.
I was rather taken with the assertion (here on the list, I forget who started
it) that one of NZ's bats was flightless. However, I've been totally unable to
verify this, and in absence of better evidence, I suggest it's a confused half-
truth (no offence intended there). NZ has 2 or 3 bat species, depends who you
ask. All are 100% endemic. The Mystacinidae is represented by the Short-tailed
bat (_Mystacina tuberculata_), a thoroughly remarkable little critter that is
adapted for both crevice-dwelling (Daniel 1979, Kunz 1982) and ground
pollination of root-parasitising plants. There may be a second species, _M.
robusta_, but I know next to nothing about it. Walker (1968) treats _Mystacina_
as monospecific. Anyhow, _Mystacina_ has been described as mouse-like in that
it is very much adapted for terrestrial creeping, being able to fold its wings
more tightly than any other bat (or 'chiropt', to use Jepson's term). In walking
_Mystacina_, the patagia are so closely appressed to the arm and hand bones that
they are barely visible. ASAIK at present, that's as close as these bats get to
NZ's other bat is _Chainolobus tuberculatus_. I haven't checked, but I think
this is a vespertiolinid. Mystacinids seem to be closest to S. American forms
(I will not elaborate or I'll be here all day), and their parasites show that
they flew over Australia (Daniel 1979).
_REFS AND FURTHER READING_
DANIEL, M.J. (1979). The New Zealand short-tailed bat, _Mystacina tuberculata_;
a review of present knowledge. _New Zealand Journal of Zoology_ 6: 357-370
KUNZ, T.H. Roosting Ecology of Bats. IN KUNZ, T.H. (ed) _Ecology of Bats_.
Plenum Press (NY & London), pp. 1-55.
MOLNAR, R.E. 1989. Terrestrial tetrapods in Cretaceous Antarctica. IN CRAME,
J.A. (ed) _Origins and Evolution of the Antarctic Biota_. The Geological Society
(London), pp. 131-140
STEVENS, G.R. 1989. The nature and timing of biotic links between New Zealand
and Antarctica in Mesozoic and early Cenozoic times. IN CRAME, J.A. (ed)
_Origins and Evolution of the Antarctic Biota_. The Geological Society (London).
pp. 141-166. Essential reading.
WALKER, E.P. 1968. _Mammals of the World Second Ed. VOL. I_ The John Hopkins
Press (Baltimore), pp. 644. Mystacinidae, with 4 photos of live specimens and
diagrams of unique thumb claw and foot, on p. 379.
Oh yeah.. dinosaurs...
"The utility of a fossil group is related directly to the amount of study is has
received and [insert your taxon here] have been neglected."