[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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



> Right, but it does show that the ancestors of ducks were present, that
> the genes in them survived into modern ducks.

Doesn't show that at all; it shows that the point of common ancestry
between modern ducks and their next closest non-duck relative is back
in the K somewhere.

I'm honestly confused and could use some clarification. How are these positions contradictory? Thanks.

The difference is small. *Vegavis* must have acquired some mutations since it split from its last common ancestor with ducks; those genes are gone.


But you're looking at this as though there was no loss of diversity, and
we can be sure there was a substantial one, both through finding
Cretaceous birds that don't have post-K/T descendants, on the one hand,
and through noting that the extant neornithine bird clades represent a
small fraction -- and not the most populous fraction in the Cretaceous
-- of the Cretaceous bird diversity.

There are no data on diversity or population sizes.

There are data on diversity... just not many.

I think you've got 'spared birds' where you should have 'a few bird
species survived'.  There was a massive loss of bird diversity.

But this is _not_ known. As has often been pointed out on this list, bird fossils are so rare as to provided only a sliver of insight into K/T ecology.

Then why do you make a strawman and say "spared birds"?

Let's for argument's sake say 5 neornithines
and 0 enantiornithines made it across the boundary.

Five what? Individuals? Populations? Species? (Five species are the minimum currently required by the fossil record; this could mean 5 populations, but never just 5 individuals.)


What are the chances that this was the result
only of luck: chance of 1 neo and 0 enanti = .5; 2 to 0 = .25...5 to 0 = 1
in 32.  Good luck, indeed!

1 in 32 is not 1 in 32,000.

Were crocs just lucky?

Probably not.

Mammals?

Certainly to some extent. Why did "pediomyids" die out but other shrew-like mammals survive?


It seems luck must be invoked when everything else fails.

The impact theory _predicts_ that dumb luck mattered.

Sure, luck could have spared some birds--but this is just another
hypothesis for now.  I think we ought to be careful how far we go
to prop up causal hypotheses.  Skepticism, and all.

That's all fine. Assumptions of dumb luck are indeed very hard to test. You are invited to come up with a better idea.


Motor-gliders, rather than continuous flappers, ill equipped to cope
with a month of global storms.

Or, they were already gone.

Why should they have been? Competition with known birds is impossible, competition with unknown birds quite improbable, predation is likewise very improbable.


Curse of the enanti's not to share this luck.

Perhaps you are exactly right.

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

Sorry. It doesn't "say" anything. It is a piece of evidence; can be _interpreted_ many ways.

How do you interpret it?