Another can, anyone?

["Colette H. Adams" <cadams@hh.gpz.org>]

Anyone up for another can of worms?

Greg Paul and others have argued against the existence of probosci in
sauropods.  However, I consider the arguments in favor far more compelling
than those against.  Here as I understand it are the arguments against:

1) There is a lack of well-developed skull processes that would indicate
points of attachment for trunk muscles.

2)  Trunk muscles develop from facial muscles, and sauropods had very
poorly developed facial muscles.

3)  Sauropod teeth are strong and well-worn, obviating the need for a trunk.

With regard to (1), I would not expect to see well-developed processes like
those of elephants.  Elephants have large, powerful trunks that largely
make up for the fact that their necks are very short and relatively
immobile.  Sauropods had enormous, highly mobile necks.  I believe that
sauropod trunks were small and relatively weak.  As for (2), many
vertebrates have fairly elaborate facial appendages, even mobile ones,
despite having immediate ancestors with no facial muscles.  Some examples
include deep-sea fishes, chameleons, twig mimic snakes, tentacled snakes,
and hornbills.  It is true that some sauropods have teeth that would seem
quite adequate for the task of clipping vegetation.  But the fact that
teeth are good for cropping does not alter the need for high rates of intake.

Consider the arguments in favor:

1) All large sauropods have relatively large external nares which occur
high on the skull.  If we look around for terrestrial vertebrates with
similar nares, we are faced with a striking fact.  The only species that
have such nares are those with probosci.  Of the species that have small,
forward nares, not one has a trunk.

2)  There is a distinct area of skull topography surrounding the external
nares in sauropods.  There must have been some kind of unusual structure
here.  It may have been a sound chamber or crest, but other dinosaurs had
sound chambers and crests without the modifications of the nares seen in
sauropods.

3)  Some sauropods have peg-like teeth seemingly inadequate for clipping
vegetation.  For an animal with such a need to consume to have such blunt
teeth is strange to say the least.

4)  Sauropods, the very dinosaurs that most needed to have high rates of
food intake, also have nares that suggest an excellent mechanism to
accomplish just that goal.  It is too much of a coincidence.  A proboscis
would have increased the rate of intake dramatically; as the mouth
manipulated one piece of vegetation, the trunk would reach out for the next.

Your comments are welcome, please resist the urge to use words like stupid,
moron and dullard, applicable as they may be.  And while we're on the
subject, those who would prefer to use this mailing list as a forum for
personal contests might consider the possibility that the world will not
come to an end if their pet theories turn out to be wrong.  I'm fairly sure
this mailing list was never intended to be an ego massage service.

Best regards,

Dave