Re: Sauropod Neck Motion

["Ralph Miller III" <gbabcock@best.com>]

 John M. Dollan <dollan@mcn.net> writes:
> The question has come up of late regarding the range of motion that
> sauropod necks were capable of.  Anyone have any thoughts on this, or
> resources at least I could look up on the 'Net?  I've heard that their
> necks were relatively rigid, that some could bend up or down, some side
> to side, some all the way around to look behind them.  Any response
> would be appreciated.

First, check out the cover story of the November 1997 _Discover_ magazine,
_Dinosaurs In Motion_, by Carl Zimmer, which profiles the work of
University of Oregon computer scientist Kent A. Stevens and University of
Northern Illinois paleontologist Michael Parrish in using computers to
simulate the movements of sauropod necks, as well as the much-discussed
sauropod tail studies by chief technology officer at Microsoft (and fellow
list member), Dr. Nathan Myhrvold.  The following concerns the findings on
sauropod neck mobility only, as Dr. Myhrvold's whip-cracking diplodocid
tail hypothesis is not the topic you chose to discuss.   

Stephens and Parrish concluded that the neutral pose for the necks of
_Apatosaurus_ and _Diplodocus_ would have been a downward slope, with
_Apatosaurus_ normally holding its head just a few feet off the ground, and
_Diplodocus_, with its head hanging down, hovering just inches off the
ground.  _Apatosaurus_ is said to have the more flexible neck, enabling it
to lift its head 17 feet into the air, swing its head 13 feet left or
right, bend its neck into a U shape to look directly behind itself, or
twist its neck into a forward facing S.  _Diplodocus_ is said to have had a
longer, stiffer neck which could only move the head 12 feet off the ground
and only 7 feet to either side.  Both are said to have been able to bend
their necks such that they could reach as far as 6 feet below ground level.
 It is suggested that this range of neck motion may have assisted the
animals either in feeding on underwater vegetation from the shore or in
assuming a tripodal feeding posture for reaching treetop vegetation (in
accordance with Robert Bakker's hypothesis).  Computer graphic analysis of
the _Diplodocus_ spine confirmed that the tripodal feeding posture was
possible for this sauropod. 

The article further states that _Euhelopus_ had a neck that could form a
270 degree arc, so that it could nearly nuzzle its rib cage. 
_Camarasaurus_ is said to have been capable of normally holding its neck
almost vertically, but _Brachiosaurus_ is said to have been incapable of
holding such a posture, as the neck's neutral position would hold the head
only 18 feet aloft, the 30-foot neck only about 20 degrees above
horizontal.  It is further reported that _Brachiosaurus_ could only move
its neck 9 feet to either side.  In addition, Stevens concluded that
_Brachiosaurus_ could reach its head no lower than 5 feet off the ground,
leading one to wonder how it took a drink.  It would have presumably had to
lower the front part of its body (as giraffes do).

Currie and Padian's _Encyclopedia of Dinosaurs_ also includes the article,
_Long Necks of Sauropods_, which may provide you with some additional
information as well.  And if you delve into the archives, you can locate
debates regarding the tripodal feeding hypothesis.

I should point out that Gregory S. Paul has also written on the subject of
sauropod neck posture, including his "Mamenchisaurus neck" post from
January 21, 1998, in which he states that the _Mamenchisaurus_ neck "was
probably held at an angle of about 45 degrees" (above horizontal) on the
basis of a specimen whose fully articulated neck is "flexed sharply upwards
at the base, just as in articulated camarasaurs." 

In his "Necks and Rearing" post of October 28, 1997, Paul disputes the
claim that a _Brachiosaurus_ neck was normally held only 20 degrees over
horizontal.  He points out that a giraffe's neck is normally held 70
degrees above horizontal, whereas the neutral position of a giraffe's
articulated cervical vertebrae would put the neck a mere 30 degrees above
horizontal.  Hence, he states, "the neutral posture is at an intermediate
angle that allows a reasonable range of motion in both directions." 
Furthermore, Paul points out that "the (_Brachiosaurus_) neck base is too
poorly preserved" to permit a proper diagnosis, and that the "giraffe-like
withers suggest that nuchal ligaments normally held it at 50-60 degrees." 
He further buttresses his case with the mention of the upwardly kinked neck
bases evident on camarasaurs, mamenchisaurs, and euhelopids (which are
taken to indicate substantially inclined necks in these sauropod groups).  

-- Ralph Miller III     gbabcock@best.com     

Up with brachiosaurs!