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Combined answer 2 Re: The extinction of small dinosaurs



Original Message by John Bois
Wednesday, 11 December 2002 13:59

> Re HP Gay's post:
> > Remember that the extinction didn't just effect dinosaurs. Most marine
> > life was badly hurt...
>
> Most marine life except...wait for it...fish?

Fish were hurt. We've had that discussion onlist. Was a short discussion due 
to the lack of ichthyologists and ichthyological literature, but still, the 
great ichthyodectids went extinct, as apparently did the small Leptolepidae, 
Aspidorhynchidae, Pachycormidae, Macrosemiidae and Semionotidae, though I'd 
appreciate more information, especially on Semionotidae; all I have is 
Benton's Vertebrate Palaeontology 2nd ed. 1997 (which is wrong in adding 
pycnodontids to the list above).

> > as were other forms of terrestrial life.
>
> Except for...wait for it...mammals,

Remember the diversity of Eutheria before (especially, but not only, in Asia) 
and after, for example. You yourself have talked a lot about the metatherian 
extinctions. South America had plenty of dryolestoids before and one known 
after the K-T. It also had the last (eu)triconodont in the Maastrichtian.

> insects,

H[orst] Aspöck: Der endkreidezeitliche Impakt und das Überleben der 
Raphidiopteren, Entomologica Basiliensia [not in Brazil, in Basel in 
Switzerland!] 22, 223 -- 233 (2000)
In German with English abstract:

"The Cretaceous-Tertiary Impact and the Survival of the Raphidioptera.
        It is a well-founded hypothesis that 65 mio. [sic] years ago [...]
        The Raphidioptera (snake-flies) [also camelneck flies] representone of 
the 
smallest insect orders with an estimated total of about 250 extant species 
(in two families: Raphidiidae and Inocelliidae), 206 of which have so far 
been described [the rest, I assume, is being described right now by his wife 
and him]. Presently, the distribution is restricted to certain arboreal parts 
of the Holarctic. A period of low temperature (winter) is a precondition for 
the metamorphosis of all extant Raphidioptera, thus the tropical regions lack 
snake-flies.
        In the Mesozoic Raphidioptera were, however, prevalent in a much higher 
biodiversity comprising also many species (genera, families) in regions with 
a tropical climate. An extraordinary rich material of fossils [sic] has 
emerged which leads to the conclusion that snake-flies were abundant insects 
in the Mesozoic occurring throughout many parts of the world and also in the 
Southern Hemisphere. Since the Tertiary, however, only those two families 
have been known which form the present-day Raphidioptera and which need a 
period of low temperature.
        It is hypothesised that the global disaster [...] led to an extinction 
of 
most Raphidioptera, in particular also of all those species (genera, 
families) which were adapted to tropical climates. Those species (genera, 
families), however, which were adapted to a cold climate could survive. 
Raphidioptera have larval periods of usually two or three years duration. 
Larvae are extremely polyphagous[,] feeding on any soft-bodied arthropods, 
but even sometimes on detritus. They live under bark or in upper layers of 
soil. The number of instars varies from about 10 to 15 depending on the 
amount of food available and on temperature, and also the duration of the 
developmental period is not fixed. These are excellent preconditions for a 
survival during the cold, dark period following the impact at the 
K-T-boundary."

The rest of the paper says, for instance, that "low temperature" means around 
0 °C or less, with tolerance down to -20 °C and less, and without it they 
don't metamorphise (and if, then not successfully); that development usually 
takes 2 or 3 years, rarely 1 year, often more than 3 years (up to 6 and 
more); and that the larvae can fast for weeks to months. All Cenozoic fossils 
belong to the extant "families"; Prof. Aspöck later told me that there are 
none at all in Messel. (Don't you think I read entomological journals. He 
gave me the reprint after a talk on impacts by geochemist Köberl. :-) )

In short, insects may be underresearched and underrepresented in the fossil 
record, but they certainly didn't all survive.

> molluscs,

Ammonites, belemnites, rudists, inoceramids are just those that I know.

> amphibians,

Bad fossil record. Remember the hype that was made in Nature about 
*Sinerpeton*, a Late Jurassic urodele? -- Does anyone know if *Habrosaurus*, 
the 1.6-m-long urodele of the Hell Creek, has any close relatives in the 
Paleocene?

> flowering plants, gymnosperms,

The secondary literature gives the number of 80 % of pollen species going 
extinct within the last 2 cm of Hell Creek Cretaceous. The conifer "family" 
Cheirolepidiaceae which apparently covered the low latitudes in the Mesozoic 
is totally unknown from the Cenozoic AFAIK.

> ferns

Contain plenty of disaster species. See fern spike.

> >...plus turning most non-saline standing
> > bodies into acidified lakes/ponds/etc...
>
> ...in which sensitive frogs could thrive.

"could thrive"? Or "just barely managed to survive"?

> > through the effects of acid rain from the debris cloud
> > (that which wasn't evaporated/boiled off during the initial
> > temperature spike)...
>
> ...which no one has any evidence for, or has ever observed.

There are acid-etched shocked quartz grains. Acid rain may also enhance the 
Signor-Lipps effect in silicate sediments like the Hell Creek Fm. And, 
remember, when there is such a big impact that, in addition, hits sulfate 
deposits, there is no known way how you could prevent acid rain! The burden 
of proof is upon you. Make up a hypothesis about how you can have an impact 
of this magnitude without (that much) acid rain. Same for the temperature and 
pressure wave.

> > Birds and _some_ mammals both have the ability to slow down their
> > metabolisms [...], and lizards, snakes, and turtles can also [...]
>
> [...] What evidence is
> there to suggest that the above strategies were not also shared by some
> dinosaur species?

None. Though neither is there any the other way around; many species were 
simply too big to hibernate; and just so minimising metabolism, as opposed to 
specialised hibernation or torpor (hibernation for a night, if you will), is 
restricted to ectotherms which probably no dinosaur species was.

> [...] 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.

Are you talking about Neornithes (about which I'd say there probably was one, 
but we know far too few K ones to tell) or birds as a whole (about which I'd 
say there was an enormous one)?

Original Message by Rob Gay
Wednesday, 11 December 2002 22:00 

> 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.

Only if that's enough to show that Placentalia, Marsupialia and Monotremata 
are primitively capable of hibernating or at least aestivating (with some 
members having lost that ability secondarily).

> 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.

Not all bacteria, of course.

> called Mokle-Membe.

Mokélé-Mbembe, or mokele mbêmbe. I've seen both in French texts. :-)

> >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.

All I know is that humans can survive for hours in very cold water, when they 
cool out faster than endothermic temperature regulation can kick in. Pretty 
dangerous, though, and we're AFAIK talking of body temperatures of 24 °C, not 
4 °C.

Original Message by John Bois
Thursday, 12 December 2002 02:09 

> Assuming the strike was an instantaneous event,

What else? :-)

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

Was that the one about the Neornithes of Antarctica? (Looks pretty bold to me 
to refer an isolated tarsometatarsus to Burhinidae. Well.) If so, it was no 
evidence of a bottleneck, but neither was it evidence of no bottleneck. :-) 
Would be great to find a lot more Enantiornithes from the Maastrichtian, for 
example.

> 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?

I'm not. Because 1.4 Ma still is a very long time. Consider what has happened 
in the last 1.4 Ma!
        (The Paleocene ended 55 Ma ago. So if it wouldn't be Paleocene, it 
wouldn't 
be close to the K-T.)

> Or, are you saying that all mammals that survived
> came from cold areas?

While I'm not, things like that may in part be true. There are crown-group 
Laurasiatheria in the lowermost Paleocene throughout western North America, 
but none have been found so far in the Cretaceous (anywhere in the world, 
while I am at it).

> > Explain to me the fern spike [...]
>
> Already established to be local effects, I thought---a fern spike in one
> location, not in another.

So you missed the discussion with HP Tim Donovan (began with the subject "How 
Did Hadrosaurs Survive?")? There is a fern spike in the USA, New Zealand and 
Hokkaido. Not sure if anyone has looked for one in the Nanxiong basin or the 
intertrappean beds of India. Apparently there is no K-T site where it has 
been shown (or AFAIK even suggested) that a fern spike is absent. (Ignoring 
those in the deep sea, AFAIK.)

> > I think that even observing it might make the data hard to record. This
> > comes from a study modeling the effects of an impact. [...]
>
> [...] the models are not calibrated enough to explain why
> enantis crashed but neos did not.

What, if anything, do we know about Maastrichtian enantis? :.-( Oh, wait. No 
enantis have been discovered in Antarctica so far, according to an SVP 
abstract on Maastrichtian neos that I dimly remember. We've had the 
discussion: Maybe everywhere else all birds were killed, and in Antarctica a 
few that happened to be neos managed to survive.

> 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,

Not only that. It explains why _all_ birds except megapodes died out at the 
K-T: because the birds destroyed each other's nests. :-) Besides, it requires 
that both parents ever leave the nest alone, and that long enough that a 
predator can discover and ruin it, and that often enough that the whole 
species dies out, and that through hundreds of species. Will put strong 
selectionary pressure on not leaving the nest alone.

> but it is an example of one of _many_ possible adaptations
> that could make life miserable for sedentary dinos.

Before you propose the next one, ask yourself "why doesn't this produce a 
mass extinction right now"?