Re: Theories on the extinction of dinosaurs

[John Bois <jbois@umd5.umd.edu>]

On Mon, 15 Nov 1999 Dinogeorge@aol.com wrote:

> Wherever the resolution is good enough, the K-T boundary clay gets the same 
> date. I think there are now several dozen sites where this is true, though 
> most are not terrestrial.

There is _no_ precise timing for the faunal changes in western interior
North America.  That is, the K/T happened only "approximately" at the same
time as the Lancian/Puercan transition (quote from Lillegraven and Eberle
1999 Vert Faun Cha through Lanc. and Pu.  Journal of Paleontology 73
691--).  In other words, where dino extinction is well recorded, we're
still guessing as to the exact time of disappearance.  And yes,
the argument that a huge asteroid hit around then, and around then all
dinos became extinct, so the asteroid must have hit at the same time--is
circular.