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NEW ZEALAND'S DINOSAURS AND THE GREAT BOTTLENECK



>  What is really pretty interesting is New Zealand. 

Anyone really interested in the history of NZ and its biota should get
hold of TREE Vol 8 (12), the Dec 1993 edition. Includes papers on moa
evolution, historical background to the evolution of the biota, and
human impact.

> I believe there's been discussion on this list that it bore fauna
> similar to those of late Cretaceous Australia/Antarctica, which it
> broke away from during the late Cretaceous. Note, however, that not
> only did nonavian dinos die out there, but mammals did as well.

??? NZ has no record of fossil mammals, bar the mystacinid
bats. Incidentally, these bats appear closer to S. American forms than
Aussie ones. That the specialized short-tailed _Mystacina robusta_ is
a pollinator of the ground- dwelling root parasite _Dactylanthus_ is
now well known (first revealed on automatic video camera!). One of the
mystacinids was apparently flightless also.  THAT'S the kind of thing
that occurs on islands lacking faunal elements found elsewhere.

All other NZ mammals are introduced. These include possums, elk and
red deer.  (Oh, presumably the waitoreke swam in.. as for South
Island's hairy man beast...)

> What NZ does have are tuataras and primitive frogs (geckos, too- did
> those raft in or were geckos around in the Late Cretaceous?) which
> did survive the K/T boundary in New Zealand.

Much of NZ's famous fauna is totally endemic, having been there since
the landmass (a bunch of accreted terranes) separated from Gondwana
about 80 Ma. If I remember correctly, this includes the obvious ones
like moa, _Sphenodon_, the bizarre _Leiopelma_ frogs, the wetas, NZ
wrens and the numerous skinks and geckos. _Hoplodactylus_ is the
famous NZ gecko - the 2 big species (_delcourti_ [up to 370 mm] and
_duvaucelli_ [up to 160 mm]) are now almost certainly extinct (a long
story), but there are numerous small, recently discovered species.
Genetic analysis suggest rapid recent speciation in both these and the
skinks, some data shows that they have been evolving on NZ for a very
long time. A number of snails and the famous NZ flatworm
(_Artioposthia_) are true endemics too (some of you may know that
_Artioposthia_ now presents a serious ecological threat here in the UK
having been inadvertently introduced in pot-plants..).

> As for ratites, does anybody have any ideas about whether they
> became flightless before or after breaking away? Were they even
> around 70 million yrs. ago?

Yup.. err, probably. Moa (that's a plural term, BTW) were near
certainly present in NZ when it broke from Gondwana. Their closest
relatives are probably emus, the case for a moa-kiwi clade now being
pretty well broken down. Kiwis, last I heard, are most probably later
invaders that came in after separation (do I need to say that they
flew in?). Moa only have a Quaternary/Recent fossil record however, so
all conclusions regarding their history are inferred from genetic
data.

>  At any rate, NZ appears to have had an extinction pattern in many
> ways similar to what we seem to see elsewhere- dinosaurs die,
> lepidosaurs and amphibians survive, or at least scrape through
> (again, does anybody have any ideas about whether ratites are part
> of NZ's original animal cargo that broke off of
> Australia/Antarctica?)

See above. On a few other points, you could (I do) take the fact that
NZ dinosaurs died out at the end of the K as evidence that diseases
*didn't* do in the dinosaurs. By latest Maas times, NZ was totally
isolated - funny how it's cargo of sauropods, theropods, dryosaur-like
ornithopods, and ankylosaurs (pterosaurs, marine mosasaurs and
plesiosaurs are also known) died out at the same time as other forms
worldwide.

Without recolonization during the Tertiary, weird and wonderful things
happened, but at the same time NZ was open to devastating events that
could 'strip down' the biota even further. In late Oligocene times, NZ
underwent a massive transgression leaving something like 18% of the
present land area exposed.  Called the 'Oligocene drowning' by Cooper
and Cooper, this event probably led to catastrophic genetic
bottlenecks in the fauna. Cooper and Cooper say something like 'This
event may explain why so little of the ancestral late Cret fauna
survives'. Nowadays, what with the extinction of the Pleistocene
fauna, about 40% of known NZ birds are extinct (see GILL & ANDERSON,
The Fossil Birds of New Zealand).

As a remarkable laboratory of island endemism, NZ's zoological
heritage is very much impoverished.

"Give yourself to the Dark Side"

DARREN NAISH