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Re: Hell Creek (long)



On Wed, 29 May 2002 21:02:38  
 MariusRomanus wrote:

>Well yes.... It's rehash of things I already knew about.... It was just nice 
>to see it in print for regular Joe Public's consumption. Just go to anyone on 
>the street and ask them what killed the dinosaurs.... Their answer is always 
>the same......"Asteroid did it."... If you say "Well, maybe, but...." they 
>look at you like you don't know a damn thing. It's always good to stir the 
>coolaide once in a while.

I just hope Joe Public isn't confused about what the Horner study really 
represents.  I see it is a good study showing how one ecosystem changed, and 
nothing more.  Give me similar studies at, oh, say sites in Europe, Asia, and 
South America, and then I will be more convinced of a gradual extinction.  If 
only that could happen...

>Smaller animals can do 
>well without large amounts of food.... crocodilians, turtles, etc.... and 
>birds can fly to better areas quickly. 

See HP Chris Lavers' excellent book, Why Elephants Have Big Ears, for a 
detailed discussion on survival habits of crocodiles.

>Large land animals on the other hand 
>have a serious problem. BUT..... What about all the small dinosaurs???? Can't 
>larger animals travel longer and farther then smaller ones in order to find 
>more suitable habitats???? What about all dinosaurs being prolific egg 
>layers.... rebounding their populations????? Oh the inconsistencies!!!

I don't think there are too many inconsistencies.  Much of what happened was 
likely related to luck, along with the abilities of crocodiles, mammals, etc. 
to hibernate, estivate, burrow, or hide. What small dinosaurs are you referring 
to specifically?  Even the smallest dinosaurs might not have had some of the 
same survival strategies as some of the other lineages that survived.  Prolific 
egg-layers?  I don't know if dinosaurs were any more prolific than any other 
egg-laying species.  Sure, some broods appear to be large, but the same is seen 
in many reptiles.  If some dinosaurs were truly "intermediate" between reptiles 
and birds in reproductive habits, then perhaps some of these large broods may 
be misleading.  Who knows what the infant mortality rates were.  It's hard to 
say that dinosaurs should have survived the KT event because they were prolific 
egg-layers.

>
>And then you have Mr. Stanford chiming in with "Trackway evidence in 
>Argentina suggests the existence of an very diverse dinosaurian fauna right 
>up to the K/T impact."...... These Argentinean 
>dinosaurs might not of had a problem with volcanics and such since the 
>weather patterns on that part of the globe kept the nasties coming from the 
>Deccan Traps and the like from effecting them...... But.... the impactor that 
>zoomed right over their heads caused them to be engulfed in the "small" blast 
>wave/melt sheet that would have shot out of the rear of the crater. Who 
>really knows???...... 

So, you are saying that perhaps these Argentine dinosaurs that Ray mentioned 
might not have been stressed at all?  Doesn't that go against the hypothesis 
that ALL dinosaur populations, and hence the entire lineage, was stressed prior 
to the impact?

>As for the rest of what you wrote..... I agree with you.... Most of what you 
>said is exactly what I had written..... You can never have enough 
>studies..... There appears to be some impact relation to mass extinctions.... 
>Compounded environmental effects from different sources conspired 
>together...... Sampling from only ONE small area of the globe and applying it 
>to the entire globe is bad mojo.....etc etc etc. The dinosaurs were around 
>for such a long time..... and they obviously put up with many changes and 
>stresses and survived them. What was taking place at the KT was just another 
>season in their 160 myo run...... It just so happens that an asteroid came 
>crashing down right in the middle of a very bad episode..... causing them to 
>lose their contract renual.... And they went off the air for good.

Yes.  I find it hard to accept those who hypothesize that the dinosaurs would 
have gone extinct due to stress if the KT event had not occurred, however.  Any 
stress that might have affected dinosaur populations independent of the impact 
was likely just another episode in their history.  Why this stress, and not 
similar stresses earlier in the Triassic and Jurassic, would have led to an 
extinction is hard to support.  But, hey, let's find more evidence!

On another note, David wrote:

>The K-T has the famous fern spore spike. The P-Tr has a fungal spore
   spike ?instead -- looks like the whole world went moldy. A marine K-T site
>in New Jersey has lots of brachiopods instead -- brachiopods had evolved
   when there still was hardly any plankton and have the lowest metabolism of
>all plankton eaters or something like that; ref: William Gallagher & Luther
   Young: Dinosaurs of the East Coast, publisher forgotten, 1995.

Yep, it appears as if brachiopods periodically "took over" as the dominant 
ocean-bottom invertebrate (mainly as some mollusks that apparently produced 
plankton-dependant larvae disappeared).  There is no mention in this book of 
what types of brachiopods took over, nor for how long they remain prevalent.  

BTW, the ref should be David Weishampel and Luther Young, Dinosaurs of the East 
Coast, Johns Hopkins University Press. :-)  Gallagher was actually the 
paleontologist who did the work that the two authors mention.  There are 
several refs relating to Gallagher's studies cited in the back of the book, 
including his Ph.D. thesis.  Maybe the easiest to find is:

Gallagher, W.B. 1990.  Biostratigraphy and paleoecology of the KT extinction in 
New Jersey.  New Jersey Academy of Science Bulletinn 34:36.  

Steve

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Steve Brusatte-DINO LAND PALEONTOLOGY
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