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Re: MAMENCHISAUR NECKS



At 05:04 PM 22/07/98 +0000, you wrote:
>RAY D STANFORD wrote:
>> By the way, moving a long, tapered neck of 19 vertebrae over any
>> practical degree of arc (especially with the vertebrae becoming     >
smaller and smaller), still requires far less energy than the moving > of a
body of two-digit or three-digit tonnage!   
>
>"Three-digit tonnage"? I think you've *seriously* overestimated the
>weight of sauropods. _Argentinosaurus_ is the only known sauropod that
>*might* fall into that category, but only Don Lessem thinks it weighed
>in excess of 100 tons. _Mamenchisaurus_ was a moderate-sized sauropod,
>certainly less than 50 tons. And don't discount the weight of that 30+
>foot neck. Anteriorly-tapering cervical vertebrae or no, that neck still
>weighed a significant amount.
>
Actually, Russell and Zheng's article (1994) give a weight of 12.6 t. to
Mamenchisaurus hochuanensis.  It was a lightweight, according to them.
This would have placed Mamenchisaurus sinocanadorum at less than 20 t.  At
26 meters, this was a large sauropod, but even it didn't come anywhere near
the estimate for Apatosaurus (at about 29 t.).  According to... (darnit, I
can't find the reference), the neck of Mamenchisaurus was very lightweight.
 It was also a very stiff neck, due to the LONG cervical ribs.

Ray Stanford wrote:
>> I notice that the photo of a re-assembled Mamenchisaurus skeleton on >
pages 36 and 37 of the book referenced in my original post gives the >
impression (even considering that there may have been some 'fish-    > eye'
lens image distortion) that the animal's cervicals taper         >
remarkably toward the head,  possibly presenting the most dramatic  >
cervical-size gradation I've ever seen in any sauropod.
>
Brian Franczac wrote in response:
>Actually, I don't think it's any more "dramatic" than in other
>sauropods, and to my eye, _Apatosaurus_ seems to have a much more
>noticeable "taper" nearing the skull.
>
Having stood in front of both of them, Apatosaurus has a MUCH more tapered
neck.  It almost looks like it comes to a point.  There is a very slow
taper in Mamenchisaurus (I just checked my pictures of it), but it does do
so. Also, Mamenchisaurus was a blunt skull (no, not the Coneheads), and
Apatosaurus had a tapered skull.  This adds to the effect of tapering,
almost to a point in Apatosaurus.


Darryl Jones         <dinoguy@interlog.com>
Visit my webpage at:
http://www.interlog.com/~dinoguy
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