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Re: If the asteroid had missed...

Michael wrote:
>Ah, but here's the rub: even if you are correct, the modern faunal 
composition probably wouldn't exist without the bolide effects, which creates a 
bit of a Catch 22.

Certainly.  However, the animals that seem to do most of the predation on 
extant large nesters (e.g., armadillos, birds, lizards) are not extravagantly 
different from pre-boundary animals.  Most explanations for the absence of 
large dinosaurs invoke preresidential advantage of current niche holders.  Yet, 
terror birds staged a large carnivorous come back in SA.  Why was this the only 
one (?).  And why did it ultimately fail?  I agree that the invaders were quite 
different from boundary types...still.  

>Of course, we've debated this point before and I know we're in relatively 
>stark disagreement about possible causal factors for higher-clade level, 
>global extinction events, as 
well as the relative importance of viviparity in mammals.

We have the bolide data.  But we still have questions that may argue for a role 
in species' interactions: why enanti's out before the boundary? why pterosaurs 
draining before?  I fully understand that the bolide was responsible for a 
great many things.  But I believe the spectacular nature of that event obscures 
the pervasive, consistent, and ineluctable quality of species' 
interactions--and the speciation they drive.