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Re: Vegavis gen. nov. - new anseriform in today's Nature



----- Original Message -----
From: "Graydon" <oak@uniserve.com>
Sent: Friday, January 21, 2005 6:22 PM

If substantiated, it also means that the chicken/duck split was
pre-K/T--mass survival.

Sure.

It shows that the chicken/duck split was earlier in the K. But how is this mass survival?


--+--Palaeognathae
 `--+--+--Anseriformes (*Vegavis*)
    |  `--Galliformes
    `--Neoaves

*Vegavis* tells us _nothing_ on how much, if at all, Galliformes and Neoaves had diversified before the K-Pg boundary.

People are generally proposing 'dumb luck'; a very few neornithine
species made it over the boundary, along with maybe *one* Gondwanan
ratite species.  (Or maybe more, but not a dozen.)

Need not even have been a ratite. Judging from the current knowledge of the fossil record one basal paleognath species is enough. Of course, this can easily mean _one population_ of that species.


It would then have to find food and a mate and food for offspring, and
the dire conditions in which to do so would last for a long time;
hundreds of generations.

_This_ is where criteria like "ability to live off seeds", "ability to live of insects", "ability to eat any organic material that isn't outright poisonous", "ability to fly", "ability to get by without food for many months" and the like kick in.


And why would one exempt na dinosaurs (especially juveniles) from
opportunistic feeding.

Because the dire ecological consequences of the event lasted for, at a minimum, a thousand years. Juvenile non-avian dinosaurs would have to reach sexual maturity in a landscape devoid of sufficient food to do so.

Note that *nothing* terrestrial with an adult body mass over 10 kg made
it.  That says a great deal about food availability.

Very well said.

And it is not just ducks, but chickens now (whatever they were in the
Cretaceous).

More or less what they are now -- jungle fowl.

(At least this is thought to be the plesiomorphy for Galliformes.)