Re: Gallery and Commentary for Copenhagen Mamenchisaurus

[DinoBoyGraphics@aol.com]

In a message dated 6/23/2004 8:27:24 AM Eastern Daylight Time, oak@uniserve.com 
writes:

> 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?)<

I think this is reasonable.  It's not that diplodocids (or other sauropods) 
_had_ to rear, but their long necks cannot have evolved for low grazing.  
Unfortunately for the thermal radiator hypothesis, neck length does not seem to 
correlate with size or paleoclimate; perhaps a statistical anaysis would find 
something though.

It would also be possible (but hard to test) that long necks were sexy 
frequently (i.e. evolving in independent linneages), acting as a handicap to 
indicate fitness in much the way ungulate antlers do today ("I'm not just a 
bull apatosaur, but I'm a bull apatosaur with a 4 meter long neck...").  There 
is (to my knowledge) no known sexual dimorphism in neck length, so it doesn't 
seem overly likely to me, but that doesn't have to rule it out.

Cheers,

Scott Hartman
Zoology & Physiology
University of Wyoming
Laramie, WY 82070

(307) 742-3799