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Re: The extinction of small dinosaurs (long again)



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.

>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.

>Dinosaurs might have hibernated.<
Well, we know that some (avian) dinosaurs are able to go into torpor.

> Most marine life except...wait for it...fish?<
I admit that I am no expert in marine paleontology, but from my
understanding, they were hurt too. Just because we have fish today doesn't
mean that none ever went extinct. We know that's not true. In fact, as long
as you still have one species of each major group that survives _any_
extinction event to get the assemblage we have today. Adaptation and
radiation happens.

> Except for...wait for it...mammals, snakes, lizards, crocs, birds,
turtles<snip>ambhibians<
Umm, I discussed this in my previous post...and IIRC, these groups didn't
come through unscathed either. That data has been discussed onlist before.

>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)

>molluscs<
Yeah, I mean ammonites, they did great! Honestly, I do not know enough about
mollusk physiology or pre-K distribution/species, etc. to comment on this
point intelligently. I'll leave that to others.

>flowering plants, gymnosperms<
I know that some modern examples have long gestation times for their seeds.
Also, I don't think these were exactly scott-free either, but I'll have to
go through pollen literature (ugh) and such to say anything more.

>ferns<
Pretty hardy things, and spores can stick around for a long time.

> fungi, bacteria<
Fungi generally like cold, dark places, with lots of decay. Trust me, I grew
up in the Mushroom Capital of the World. Bacteria are hardy things as well,
and can survive in decay, as well as in geothermal springs (geysers and the
like) for a long time. I doubt that geothermal processes would have been
greatly altered by an impact, so I don't see why bacteria living there would
have any problem.

>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.

> 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.

> Most of the creatures that "survived" were small.  Their lack of
"efficiency" didn't hurt them.  "Efficiency" needs definition, I think.<
Small endothermic animals are poor at retaining energy collected. It is
burned rapidly by digestive and other vital (respiratory/circulatory)
functions, and owing to their surface to volume ratio, a good portion of
their heat escapes to the atmosphere. Lumbering animals also burn energy
rapidly with their internal processes, but not as rapid (compare the average
heartbeat of a mouse to an elephant). Plus, their size helps trap any heat
energy that would otherwise be lost to the outside air. The only way that
small endotherms can get around this treadmill, so to speak, is to either go
into torpor, or hibernate. This allows their internal processes to slow
down, so that they are burning energy at a much slower rate. Yes, they still
lose energy to the air, but the energy being lost internally is greatly
reduced.

> 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.

> 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.

> ...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).

> ...in which sensitive frogs could thrive.<
See my previous post on frogs and hibernation.

> ...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.

> Total speculation...may or may not be true.<
Unless the dinosaurs didn't die, or their corpses were vaporized, I would
imagine that dead dinosaur bodies would mean carrion.

> 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.

> Look, all animals species _but_ dinosaurs survived!<
This is blatantly false. Even not looking at the previously mentioned taxa,
I think it can be shown that _no_ species of mosasaur survived, for example.

>mammals that don't hibernate cannot be induced to.<
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.

>Also, what evidence is there that suggest _only_ members of species that
hibernated survived...<
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.
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.

> The elimination of one hypothesis (I also reject the disease hypo) doesn't
validate the favored hypothesis.<
Oh, I agree, but it does limit the potential causal agents. But the main
reason I mentioned the disease hypothesis is because someone in an earlier
post had brought it up, and I thought I should address it, that's all.

>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?

>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.
I would also recommend reading over HP Williams' and Chip's posts on the
subject, as well as the link (repeated below) from HP Edels.
http://www.cmnh.org/dinoarch/2000Mar/msg00398.html
Peace,
Rob
Another cookie for those who managed this tome as well. ;)

Student of Geology
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