Re: Late K sauropods, Trachodon, teeth?

[sean.kerns@sdrc.com (Snake)]

> 
[some stuff deleted]
> BTW, the reason "Trachodon" was abandoned was that the type material
> included both hadrosaurid and ceratopsid teeth.  So, actually, Leidy
> described five major components of Late Cretaceous western North American
> fauna with just four teeth! - tyrannosaurids (Deinodon), troodontids
> (Troodon), ankylosaurians (Paleoscincus), and hadrosaurids & ceratopsids
> (Trachodon).
> 
>                               
> Thomas R. Holtz, Jr.                                 
> tholtz@geochange.er.usgs.gov
> Vertebrate Paleontologist in Exile                Phone:      703-648-5280
> U.S. Geological Survey                              FAX:      703-648-5420
> Branch of Paleontology & Stratigraphy
> MS 970 National Center
> Reston, VA  22092
> U.S.A.
> 
> 

I know this is going to be a horribly amateurish question, but keep
in mind I'm a historian, and I'm used to having lots of documentation
behind what I research.
This idea of describing species based on partial remains has always
seemed to me to be a little, well, hypothetical, but I figured, 
paleontologists must know what they're doing, so I pushed it out of
my mind.
But this last post just pushed it right back in, so I gotta know:
I know it's possible to make pretty good (educated) guesses on
missing parts of an animal if you have some of the pieces around it,
but how on earth can you possibly construct an entire animal based
on a tooth???
If you say "This looks very close to the teeth of this thing over
here, which we have much more complete remains of," how do you
determine whether you have another species vs. more of the same?
And if you determine that it's probably a similar species, then
how can you determine how the difference in that one piece would
affect the appearance of the rest of it?
And if you don't even have something else similar to compare it
to, how can you go about constructing a whole animal around that
tiny little piece?

I have heard of dinosaur species known only by a claw, or a tooth,
sometimes even only a footprint. And then I find out that all 
these Brachiosaurus (or is it the  Brontosaurus) pictures I see
are based on the one top part of the skull that we've found, and that 
up till we found that one, we'd had somebody else's head on there?

Is it really all as speculative as it seems, or are you really 
able to make those leaps based on previous information?

Disclaimer: I'm not doubting your abilities or expertise; it just
all seems all so intangible. Thanks for letting me ramble.

Sean



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