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Re: Triceratops sprawl



On Thu, 1 Feb 1996, Rob Meyerson wrote:

> >(big snip)The problem is this:  EVEN BIPEDAL 
> >ORNITHISCHIANS HAD FORELIMBS MOUNTED DIRECTLY UNDER THE BODY.  
> >Ceratopians would have had to evolve a sprawling posture deliberately, as 
> >it were, because they inherited an erect forelimb posture from their 
> >bipedal ancestors.
> 
> That's the point I am trying to make.  Ceratopians purposely evolved 
> sprawling forelimbs to better cope with the paleenvironment of the Gobi (an 
> arid environment with many dune fields).  When one considers how effective 
> the ceratopian body plan was for efficent movement in the dunes, it makes 
> perfect sense why they would evolve sprawling forelimbs, while leaving the 
> hindlimbs vertical.  The dinosaurian equivalent of the dune buggy, if it were.
> 

There is a rather sizable hole in your argument:  big neoceratopians (the 
ones that are supposed to sprawl) don't show up in dune sediments!

The numerous land connections between Asia and western North America that 
occurred near the end of the Cretaceous (Dinogeorge notwithstanding) mean 
that they certainly *could* have spread back into Asia.  After all, 
protoceratopids of Asian mold show up in latest Cretaceous North 
America.  Apparently the big ceratopids *disliked* the dry dune 
conditions prevalent in east Asia.

I also have trouble seeing how sprawling forelimbs make for a very 
effective "dune busting" mode of locomotion.

Nick Pharris
Pacific Lutheran University
Tacoma, WA 98447
(206)535-8204
PharriNJ@PLU.edu

"If you can't convince them, confuse them." -- Harry S. Truman