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Re: dem bones

"Considine, Blaise" <bpc.apa@email.apa.org> writes: 

>Now my question is why can't you tell how the bones ought to be 
>Don't bones line up in one correct way? 
>Couldn't you tell about the ribs from their curvature (or what is left 
>after fossilization)?  

I can't speak about the ceratopsian bones, but from what I have seen of
hyoid bones on mammals [hyal bones are often called "neck bones" or "tongue
bones"], unless you have a living example to use as a model, trying to
"reconstruct" a fossilized hyoid apparatus is EXCEEDINGLY challenging. In
living mammals, the ends of the hyal bones are covered by a thick layer of
cartilage, which holds the entire apparatus in it's correct position.  The
bones don't touch each other.  In fossil mammal hyoid apparati, the
cartilage has rotted away.  There are "articulation facets" on the ends of
the bones, which give some clue to the angles at which these bones were
attached to each other.  But, unless you have a dissected apparatus from a
Recent mammal to examine, you cannot be sure that the reconstruction is
close to "true" accuracy. 
  What little I have read on the bones of dinosaurs suggests that dinos had
a rather thick cartilage layer between bones.  So, trying to fit the bones
together like a jigsaw puzzle is not always going to give you the best
approximation of the animal's bone orientation.
  Ball-and-socket joints are easy.  It's the bones that articulate on flat
surfaces that can give you headaches.