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



> 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"?

Don't understand the question. Birds weren't supposed to be spared, except for a freak, lucky, single flock, as I remember Feduccia's crab-cracking shore birds. But it seems to be more complex than this now. If enough _different_ birds made it across, they were, in a sense, spared.

"Enough different birds" means one viable population per species, of at least 5 species. This can amount to _very_ few individuals. Especially if you take the postapocalyptic world into account -- practically no predators, no competition.


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

I know luck plays a role. But I'm not sure why one would invoke it in any specific instance--I mean, one would have to rule out other causation--and we know so little.

Haven't we ruled out all other proposed causes in these cases? :-) (Actually, we haven't. Different susceptibility to pyrotoxins or to fungal infections could have played a role. These are just as untestable, though.)


The impact theory _predicts_ that dumb luck mattered.

I think not, unless you mean dinosaurs were unlucky to require big amounts of food. Otherwise there is a kind of surgical strike quality about it.

_Of course_ the impact theory predicts that dumb luck mattered. It predicts continent-scale wildfires -- something may have been in places that didn't burn. It predicts humongous tsunamis -- something must have been in places where the tsunamis didn't reach. And so on.


The best comparison might be: Line up a lot of people along a wall. Then give the execution squad imprecise shotguns that strew a large amount of small bullets in rather random directions. Give them one shot. Someone is going to survive because no pellet happened to hit a vital organ of theirs.

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

I think species interactions are common and well-observed phenomena in extant communities. they cause extinction, etc., etc.

Problems are: - They ae much less well observed and studied than you seem to think. - They have never led to _mass_ extinctions in known cases.

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

We have discussed this long and hard before. Don't think you have absorbed/validated any of my points.

I have understood your points, and none comes close to convincing me.

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

Perhaps you are exactly right.

Again, it is highly unlikely that several members (pops) of one clade made it through and none of another did.

No, it is not, because your calculation has a serious thinking error. It isn't "how probable are 5 out of 5 vs 0 out of 5". It is "how probable are 5 out of many millions vs 0 out of many millions". There's practically no difference there.


In the presence of extant mammals and birds, large egg layers are unable
to make a serious go of it.  Large egg layers have not _surrendered_ these
niches, they are unable to enter them.

Just about _everything_ is unable to enter an _occupied_ niche!

There are exceptions to this--but
they tend to be in places of low predator (mammal and bird) density.  I
think the revolution in bird and mammal abilities toward the close of the
Cretaceous had something to do with it...and that they continue to have an
influence in reducing the viability of > 10 kg. egg layers.

I'm going to tell you something. Another listmember has recently seen a lioness on TV that tried to crack an ostrich egg. She just managed to clamp her jaws around it, but found herself incapable of biting -- her jaw muscles were so overstretched. Eventually she dropped it unharmed. Now please explain how a mammal the size of _at most a cat_ is supposed to crack a hadrosaur or sauropod or tyrannosaur egg.


I guess this is how ostriches survive in the presence of _high_ predator diversity.

And then come the success stories of dromornithids, phorusrhacoids... perhaps gastornithids count, too.

Now, where is the revolution in bird and mammal abilities toward the close of the Cretaceous? *Cimolestes magnus* is much smaller than *Repenomamus giganticus* which lived some 70 million years earlier. And if you're looking for a predatory terrestrial bird from the Late Cretaceous, I can merely recommend *Avisaurus*.

I recognize the importance of the bolide, the instability of the
global habitat.  But I think it lacks predictive power, especially
now that birds seem to have survived in greater numbers!

Those numbers are still tiny, as I've tried to explain several times now.