Re: "But What About The..." arguments Re: dinosaur-centred extinction models

["Steve Brusatte" <dinoland@lycos.com>]

On Mon, 03 Jun 2002 19:21:37  
 David Elliott wrote:
>And Steve Brusette added:
>
>>1) As David mentioned, even if dinosaurs did spread diseases between one 
>>another, this does not explain the extinction of mosasaurs, rudists, 
>>ammonites, forams, etc.  I once asked Bakker about this in an interview and 
>>he didn't have anything to counter the argument.
>
>Regarding Robert Bakker, he DID actually talk about the extinction of all 
>those other critters (in TDH), although in my lurking i've noticed that his 
>extinction-model seems to have been inadvertently edited (in this particular 
>conversation), unwittingly creating the impression that he didn't: His idea 
>wasn't just "diseases spreading to places they haven't been before", which 
>is kind of the impression you get from recent comments - that was one part 
>intrinsically tied in with a larger model. And it's the larger model that 
>accounted for the extinction of those that (we're assuming) went along with 
>the dinosaurs. (unless, of course, he has since withdrawn everything about 
>his model except for the dinosaur-disease bits) (pages 440-444 The Dinosaur 
>Heresies)

My apologies if I have skewed Bakker's hypothesis in any way.  It's been a long 
time since I've read TDH, and I was just going by the interview that I did with 
him (in which he didn't offer any type of larger model...I wonder why?).

In my opinion, the assumption that the extinction of the mosasaurs, ammonites, 
rudists, etc. is directly correlated with that of the dinosaurs is not only 
valid, but necessary, much like the assumption of parsimony in cladistics.  As 
Nick Longrich mentioned a few days ago, the odds of an entire lineage of 
animals disappearing independently of several other lineages around the time a 
freakin' huge bolide collides with earth is astronomical, pardon the pun!  

>To a vaguely related topic that i just thought i'd raise while i was here - 
>how strongly linked are the extinctions of mosasaurs, foraminifera, 
>plesiosaurs, etc etc..?
>
>Have statistical studies been done into the probability of 'everyday' rounds 
>of extinctions occurring, by chance, during other larger extinctions to 
>create the impression that they're related when they're not (and how sure 
>are we of timing, btw? It seems to me the chance of this is increased when 
>you consider that we can't always tell *exactly* when something 
>dissappeared)? Im just thinking, if stegosaurs had happened to delay their 
>extinction until the end of the Cretaceous, we'd assume they were part of a 
>mass extinction that they might not have been. 

Hmmm....maybe.  But, we must remember that stegosaurs were only a small 
fraction of the Dinosauria.  It's much easier for smaller groups to go extinct 
than it is for a large and diverse lineage.  In regards to statistical studies, 
I'm unaware of any that have really crunched the numbers.  But, I may be wrong.

>Is it possible that, say 5-15% (just pulling a figure out of my sleeve for 
>the sake of argument, theres no meaning in those numbers) of some mass 
>extinctions are just coincidence - actually, isn't it almost *certain*?

Maybe.  But, again, the Dinosauria is a very large group.  Explaining its 
extinction as "background" is dangerous, IMHO.

Steve

---
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Steve Brusatte-DINO LAND PALEONTOLOGY
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