Re: Gallery and Commentary for Copenhagen Mamenchisaurus

[Graydon <oak@uniserve.com>]

On Wed, Jun 23, 2004 at 11:26:36AM +0100, Mike Taylor scripsit:
> So the basic problem of sauropod neck posture is that the morphology
> seems to tell us one thing, whereas energetic and evolutionary
> considerations tell us another.  If you can resolve this
> contradiction, you will make me a happy man

Three semi-sensible things and a wingnut idea  --

Neck length and tail length were somehow developmentally related, and
tail length had vital defensive or breeding display uses.  (I think this
one is weak, given the variability of neck lengths and tail lengths and
the probable postures for either.)

Apatosaurs and diplodocids generally are prime candidates for rearing to
eat from tree crowns; is there a way to tell the difference between a
horizontal neck posture in a quadrupedal stance and a vertical posture
in a bipedal stance?  If there isn't, the 'horizontal' result is
consistent with high feeding.  (There's also the consideration that in a
semi-arid environment, the good stuff, food wise, is on small patches of
wet ground you don't want to stand on if you weigh that much; perhaps
being able to reach in while securely supported was extremely
important.)

It has been hypothesized that getting monstrous big in the first place
was a response to cyclical aridity; the long neck may have allowed for
water scavenging from the breath, low-effort mechanical blood pumping
due to side-to-side motions while walking, or some other source of
energy efficiency (heat exchange?)

My own take on the matter is that large birds with long necks have in
some instances completely smooth neck vertebrae; I'm thinking of a Great
Blue Heron skeleton the ROM is planning to mount next to a Dienonychus
for comparison purposes, but there are others.  Given that these are
birds which have muscular necks which are a primary part of their food
gathering strategy, I think there is something we don't know about the
biomechanics which is throwing most of the hypothesizing off.

-- 
"But how powerful, how stimulating to the very faculty which produced
it, was the invention of the adjective: no spell or incantation in
Faerie is more potent." -- "On Fairy-Stories", J.R.R. Tolkien