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Re: The extinction of small dinosaurs (long again)




On Wed, 11 Dec 2002, Rob Gay wrote:

> John Bois wrote:
> > Mammals that don't hibernate cannot be induced to.  Most mammals in
> "equable" climates don't hibernate.<

> So? Some mammals do hibernate, and that's what's important here. Admittedly,
> we can't know exactly what physiological adaptations the K mammals had, but
> as some mammals today are able to hibernate, it stands to reason that K some
> mammals were able to hibernate/go into torpor.

Are you proposing that _all_ surviving mammals are relatives of K/T
hibernators?  I think you are.

> >Birds don't hibernate.<
> That's right. They can go into torpor, which means that they have the
> ability to lower their metabolism, so they're able to reduce their food
> intake.

OK.  By how much?  For how long?
 
> >Dinosaurs might have hibernated.

> Well, we know that some (avian) dinosaurs are able to go into torpor.

Doesn't that put your hypothesis at risk?

> >insects<
> I'm no insect person, but I do know that extant insects can survive for some
> time in a dormant state (just watch WWD, and see it for yourself! That's a
> real insect that's frozen there)

Assuming the strike was an instantaneous event, only those bugs that had
already oviposited...i.e., only bugs of one hemisphere's temperate/arctic
zone...would have re-emerged after.

> >And, don't forget, "if".  Extinctions attributed may not belong--birds, for
> example.<
> Indeed, the Signor-Lipps effect is an important one to consider. But show me
> hesperithorid fossils after the K/T. Or icthyorid remains. From my
> understanding, there's a lot of evidence pointing to birds being badly hurt
> too.

One of the talks at the last SVP addressed this point and found: no
evidence of a bottleneck in birds.

> > Circular...it must have happened so whatever happened, happened.<
> Well, we know that a bolide hit the earth (unless that's a giant's footprint
> down in the Yucatan). Unless you can show me that physical models of the
> impact effects are wrong, conclusively, then we need to explain why what
> survived did indeed survive. Do modern plants have adaptations that would
> help them survive a similar event today. Yes, in some cases, they do. It's
> logical, then, to assume that some plants back then, related to those today,
> would share these adaptations.

Well, this is an eminently testable hypothesis!  But, let me warn
you...full flowering forests are found fairly close to the K/T (Paleocene,
I believe).  Are you prepared to be falsified?

> The only way that
> small endotherms can get around this treadmill, so to speak, is to either go
> into torpor, or hibernate.

Since all endotherms that survived are small, all survived by going into
torpor or hibernating.  So, you're saying that mammals that survived in
Hell Creek--even though this was a warm area and they probably didn't
hibernate--hibernated.  Or, are you saying that all mammals that survived
came from cold areas?

> > This is contra my experience.  I have a dog and a cat that sleep most the
> live-long day...were small dinos more like them or gnawing furball rats?<
> I too have a dog and a cat, and they to do indeed sleep a lot...but they
> still eat several times a day, every day.

Illustrating its bad breeding, my dog eats poop: now, there is a scenario
for you...

> > What else is there?  They don't have to study for exams.  And mine has no
> gonads.<
> Nor does mine. But in a domesticated setting, things to do are rather more
> limited in scope as opposed to if they were wild.

I have to give on that one.

> > ...not established!<
> Explain to me the fern spike if in fact not most of the groundcover
> (photosynthesizing plants) were removed in one fashion or another).

Already established to be local effects, I thought---a fern spike in one
location, not in another.

> > ...which no one has any evidence for, or has ever observed.<
> I think that even observing it might make the data hard to record. This
> comes from a study modeling the effects of an impact. I can provide a
> reference if needed. If you want to dismiss  that, its fine, but since no
> one actually saw the dinosaurs die, we might as well say there's still one
> living in Africa called Mokle-Membe.

You have a point, but, the models are not calibrated enough to explain why
enantis crashed but neos did not.  If they can't do that, I don't know
that I trust the Armagedon for all.

> > All frogs?  Or just the species from unequable climates that have adapted
> over time to do this?<
> No, not all frogs. But I know spadefoot toads here in Arizona can do it, I
> know that some can be frozen, and I know that some salamanders can remain
> buried for years. So its not just cold climates or such...these things exist
> in many places.

OK.

> I have been told that under certain conditions, humans can go into torpor,
> because it was an adaptation that we possessed, but are in the process of
> losing due to our modern society.

For 20 minutes, right?

> I'm just looking at what survived, and looking at the survival strategies of
> those modern relatives. And, as I said before, in my earlier message, the
> ability to hibernate/go into torpor is the only characteristic that I can
> see some members of all the groups that survived. Metabolisms, reproductive
> strategy, niche, etc. are all different for the groups in question.

I think you have some testable hypotheses for sure...

> Torpor/hibernation is what seems to unite the groups.
> 
> > How do you know this?<
> I never said I "knew" it, I said I thought it was likely. And I say that
> based on the evidence that I see.

Fair enough.

> >it is quite possible that behavioral strategies of birds assisted in
> knocking off small non-avian dinosaurs<
> I fail to see how this is testable, let alone a feasible idea to begin with.
> We know birds and non-avian dinosaurs coexisted since at least the late
> Jurassic...why not "knock them off" before the terminal K?

Invasions have caused much extinction today...new birds either evolving
sympatrically or allopatrically may have developed new strategies that
were effective against little dinos.  For example, the ability to take off
vertically might allow a predator bird to stay longer at a nest, and,
perhaps, escape scot free upon the parent's return.  I know this is pure
speculation, but it is an example of one of _many_ possible adaptations
that could make life miserable for sedentary dinos.  And, I find the claim
that nothing changes in the biota unless a catstrophy occurs to be
unfounded...stuff happens all the time.

> >There are predictions taht are in the process of being
>  tested.  Example: was there or wasn't there a bottleneck in bird species at
> the K/T.  You would say there was, I would say there was not.<
> I am very skeptical of studies showing population densities and relative
> abundance, etc. The fossil record is imperfect. For example, you could say
> you have a study showing an increasing number of genera in group A through
> time until the K/T boundary...but you're sampling from a very limited
> habitat (probably a floodplain). A whole different situation could be
> occurring in montaine environments, or desert, or polar, or any other poorly
> to unrepresented paleoecosystem (okay, so deserts have a decent preservation
> potential). Not everything gets fossilized to begin with, even in the
> floodplain. Without a time machine, I doubt we'll ever really get to know
> true population densities and ratios between groups. We just don't have that
> resolution in the record.

But, even presence or absence of fossils can bear on the argument--I mean,
if I understand correctly, "bottleneck" here refers tp a species die off,
not that of a population.

That's _two_ cookies--or, do I have to agree to get the cookies?  OK, I
agree.