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