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Re: OUR FRIEND, THE KIWI
On Wed, 13 Nov 1996, Paul Willis wrote:
> I really don't think that you are using suitable caution here in your
> comparisons. Apart from scaling effects, there are details that you seem to
> gloss-over. Eg: From what I have seen of the Chinese bird-dinosaur, there
> is a single row of short, rounded projections along the back that could be
> the imprints of feathers.
Not just along the back, though!
Close inspection reveals, contrary to
published restorations, that the _impressions_ of feathers exist on the
underside of the neck. Remember, you are only looking at ONE of the two
pieces of this fossil! It is very probable that the actual feathers
themselves are present on the complementary piece. Also, the restoration I
saw seemed to only show feathers along the spine, I think this is wrong
because the other creatures I saw- the longtail birds- were splatted kind
of like a Wile. E. Coyote impact, arms and legs splayed, preserving
feathers along the side but not along the spine. The best explanation is
that both animals were feathered all over but that fossilization has only
preserved feathers in the plane of the rock, and that some of these
feathers are on one slab, and others, on the other.
> While I do agree that some modern birds such as the kiwi do have many
> structural similarities in their hind limb structure with those of
> theropods, I urge a high degree of caution when trying to use such
> similarities in the reconstruction of extinct animals.
Roger that, kiwis are in many ways unusual birds. Some of these
may be due to living on the ground, but others may be due to the unusual
environment and ecology of New Zealand. Certainly, mesozoic ecology would
have been very different, if only because there would have been
ground-living predators, which New Zealand appears never to have had. This
alone probably opens up who new possibilities. And the fact that there
aren't things like varanid lizards or carnivorous mammals either, which
will eat young and eggs, probably makes the selective pressure acting on
kiwis very different. I don't think that the tuatara i a
voracious predator of eggs and chicks.
As for mammals being crowded out- the existence of flightless bats
and wrens in NZ history implies that there certainly have been vacant
niches that small mammals could have filled admirably. It is possible that
the islands at one point were so far underwater as to be too small to
allow mammal survival, but at bare minimum, the
following ecosystem must have existed: two ratites (one for a moa
ancestor, one for a kiwi ancestor) one gecko, one tuatara, and a frog
(there could be other things as well, I'm not that up on the zoology of
the place). An island that would be large enough to support the two
species of ratite, the tuatara and the frog would seem to me to be large
enough to support a small mammal, but I could be wrong.
Does anybody know what the minimum size of the NZ landmass was?
Incidentally, if anyone hasn't heard, the Kiwi egg is
_not_ a leftover adaptation from Moas as Gould has stated, kiwis
aren't even all that closely related to them. I think this is one
reason why Gould pisses some people off: "Oh, the Kiwi egg has no
adaptive significance, it's just a random accident of evolution". If you
have the view that who lives and who dies is more or less random, and that
a lot of adaptations are just random, then if you run into a puzzle, it
gives you an easy way out: "Oh, you're just trying to use the failed
paradigm that all adaptation must be functional".