[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: More on Argentavis
> But if we do NOT find any volant ratites, and fossil
> flightless ratites keep
> on piling up, then you can still argue that your
> hypothesis has not yet been
> refuted. You could claim that fossil volant ratites
> existed, and we just
> haven't found them yet.
> In short, the "absence of evidence is not evidence
> of absence" argument
> works in your favor, but not in mine.
Ah, I'm trying to avoid that. Slap me if I don't.
Thinking of Africa's lack of Paleogene avian fossils
helps if I get brash...
The hardest thing is not to get overwhelmed by
evidence. Having a hand-list of blanks - like Robert
T(IIRC)'s idea of "list of sites which *lack* key
fossils one would expect" - helps too.
As regards the other Meso/Early Cenozoic taxa -
In a nutshell: I shamelessly expanded the scope. There
is no untried data crownwards. But ratite
flightlessness - convergent or not - must derive from
*somewhere*, *somehow*. Knowing more about
paleognath/basal neornithine patterns of evolution,
biogeography etc certainly can't harm. _Limenavis_ for
example is useful as an outgroup that's very close to
the interesting bits.
(If one is really extreme, _Gargantuavis_ cannot miss
;-) If one wants to add that... thing..., one might
just as well throw in _Patagopteryx_ - if anything
groups with *that* unduly often, you'll know a
character needs to be refined or removed.)
For the time being, there is little else to do with
the data at hand; about any reasonably possible
phylogeny has been proposed, and few could actually be
rejected, so one might just as well fool around with
the data a bit. Not to prove or disprove anything,
because that seems just impossible at present; only to
observe how it behaves in its probable phylogenetic
"environment". Might even help pinpointing promising
I have checked on the molecular studies since the data
started to become good (ancient DNA, decent-length
sequences) and *something* is odd about it. Can't lay
my finger on it... might be a bad signal-noise ratio,
might be an apomorphically altered metabolism adding
noise, or whatever. Still, the moa sequence
divergence, which should be comparable with with crown
taxa, is odd. Morph/mol evolution rates don't seem to
match up. Massive genetic drift, with Taupo volcano
blowing up ever so often again? I don't know...
It's almost as bad as with the hoatzin. However, with
ratites, there are at least ample taxa known or
suspected to be close.
> Australia is certainly BIG. New Caledonia is
> decently sized. But Fiji ??!!
Don't know how much exactly you'd have to lower the
sea level/lift the channel between Vanua and Viti to
make them connect, but as soon as they do (especially
with lowered sea level) the resulting landmass is in
the league of NC. Fiji is actually a distinct
mini-plate, with a tiny shelf etc.
BUT this is only relevant from the Late Miocene
onwards, as there was little Fiji at all before that
(Given that, I'd say yes, it was probably a
micro-continent - possibly more dry land than NC even
- several times between c.8 mya and today). See e.g.
for the interesting relationships between
Indo-Australian and Pacific plates around Fiji.
BTW regarding flightless birds: is the second species
of _Pachydyptes_ (the heavyweight penguin) still
__________________________________ Wissenswertes für Bastler und Hobby
Handwerker. BE A BETTER HEIMWERKER! www.yahoo.de/clever