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

Nest guarding would be a must in my view.  Provisioning hatchlings might
be difficult given the size disparity.  But then again, a small
regurgitation would be mana from heaven for a throng of hatchlings.

True, but guarding and feeding the young do not imply each other. Think crocodiles -- they guard but don't feed, perhaps due to the size disparity.

The evidence from TE
Martin's study suggests that if organisms have their druthers (i.e.,
if predation pressure is lower) they will invest more in fewer offspring.

Doesn't this depend on whether the predation pressure on adults and juveniles is the same?

...you're looking at ten _thousand_ eggs, and pretty good odds two of
them make it to stable reproductive adulthood, on average.

There may be a faulty assumption here: predators and prey control each other's population levels with a negative feedback system. But ecosystems are not super-organisms taking care of their health. No doubt population oscillations occur and that they are caused by food availability/predation, etc. But there is no reason to assume _a priori_ that predator populations could not eat every last one of a brood of even thousands.

The trick is to release all thousands at once, and to do this so seldom that a large predator population can't wait for the next such event to survive.

I'm not knocking ostriches.  They are exceptional birds.  Indeed,
given their amazing speed and immunity from predation as adults,
they embody a fundamental evolutionary challenge: why didn't
dinosaurs re-establish dominance in the large animal terrestrial niche.

I guess mammals were simply faster to fill most of these niches, starting from the K-Pg boundary when they were all empty.

Concealment?  Small offspring could hide, but not that well
if guarded by parents. I guess my point, finally, is that creatures
cannot just keep uping the offspring numbers indefinitely...

I can't quite see the difference between "indefinitely" and "for 150 million years".

and that this limit plays a role when organisms in similar
niches are competing with each other.

Could you find an example of such organisms?

And the upshot of this (potential) fact of evolutionary life, is that the
diversity of organisms practicing parental investment has increased!

Perhaps this is just a side effect of the fact that the diversity of Placentalia has increased.

Which is all it really takes, and being a huge R strategist is quite
cheap, energetically.

I don't think this computes. A pine tree invests way more than a flowering plant in its reproductive effort (right?).

No idea. Pine pollen are most probably cheaper than angiosperm pollen... I'm not sure about the seeds.

Sixty million years of mammalian predator ecologies, and at least ten
million of dinosaurian predator ecologies.  That's as well or better
than pretty much anything else that's fully terrestrial is doing.

Truly! And yet check the minimal diversity of the body plan. There has to be a reason for this--beyond waiting for a mass extinction as per David M's. world view.

Assuming I understand "minimal diversity" correctly... why do you think there has to be a reason for this, other than the fact that Placentalia survived the K-Pg boundary for perhaps totally different reasons?

Since people have subsequently found quite a number of Cretaceous
sauropods, it's far from clear that their diversity declined.

Is nothing sacred?

In science?