Re: dino listing

["Andy Farke" <andyfarke@hotmail.com>]

Replying to Dinogeorge's: >What
might the 12 genera right at the Hell Creek/Cenozoic boundary be? I'm 
pretty sure _Tyrannosaurus_ and _Triceratops_ qualify, also 
_Pachycephalosaurus_, _Stygimoloch_, _Ornithomimus_, and maybe 
_Ankylosaurus_. How about_Thescelosaurus_? _Ricardoestesia_? 
_Torosaurus_? It's pretty easy to compile a list of North American 
Maastrichtian dinosaurs (see, for example, the stratigraphy section of 
_The Dinosauria_), but figuring out which of those might be the very, 
very last ones known is a bit trickier. (Unless of course you find the 
right paper.)

I don't know if it is easy (or possible) to determine what these 12 
genera might be. Many of those mentioned (e.g., Torosaurus, Stygimoloch, 
Ankylosaurus, et al.) are rare below the boundary, let alone AT it. 
Also, I have a hunch that some animals in the same family (such as 
Triceratops and Torosaurus) may be confused or misidentified when 
collected (such as that awful problem with any Maastrichtian ceratopsid 
fragment being referred to Triceratops). Then, there's that nasty 
problem of inflating/deflating species counts depending on the opinions 
of the investigator (e.g., Triceratops horridus vs. Triceratops 
prorsus). Could local environmental changes (such as mountain building, 
change in climate) affect bone preservation? Could this skew counts?

It's nice that they're tracking dinosaur diversity in the Hell Creek of 
Western North America, but what about the rest of the world? How was 
diversity affected in Asia or South America? Or even the American 
Southwest? Did all dinosaurs world-wide go extinct simultaneously? Were 
there variations between northern and southern hemispheres? This was a 
global extinction, and I doubt much more progress will be made (at least 
in the land animal area) until global faunal counts are done. Does 
anyone know if this has been done yet?

Looking forward to input on this,
Andy Farke

The Torosaurus Home Page
http://www.geocities.com/CapeCanaveral/Hangar/3404
andyfarke@hotmail.com

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